Rotate shapes about the origin with exact matrices
Construct rotations from their angle and direction,including quarter turns and exact30°,45° and60° entries,in all four practice modes.
Exam scope and assessment notes
Original Mathematics B Matrices5A–G candidate: twelve teaching lessons,twelve worked examples,36 explained guided/independent/application practice tasks,and48 bound four-stage cases;all four specified reflection lines,rotations and enlargements have dedicated complete four-stage bundles. Matrix data,addition,multiplication,scalars,identity/zero,nonsingular2×2inverse,and plane transformations retain their own original givens. The learner enters blank working operands,intermediate results,constructions and separate final answers;edits,withdrawal,clearing,stage/reset and source/session/revision changes withhold old comparisons and explained references. Exact supported real square-root entries cover30°,45° and60° rotations in addition to quarter turns;the general cosine/sine formula is taught,while more general numerical trigonometry and equivalent forms outside the finite algebra engine require review. Written meanings,dimensions,units,geometric descriptions,drawn shapes and empirical validity need human review. All7Matrices source rows have reviewed structural teaching/practice bundles only while every original complete record remains intact. Row5Fjointly requires all six named transformation-family records,each with all four stages. Other Mathematics B source rows remain unlinked; see the current course map;the wider Pearson curriculum remains incomplete. ISBN9780435044107 is metadata only;no full book body,chapter sequence or Hub mapping is verified. Single Higher-tier linear4MB1;entry context November2026/June2027only. No MathematicsA,Foundation,modular or later-series inheritance. No fresh mounted-browser,hosted four-stage interaction,saved progress,official marks,mastery,specialist approval or formal assessment readiness is established.
Before you begin
- Signed exact rational arithmetic and fractions
- Rows,columns and labelled coordinate pairs
- Original matrix orders and row–column multiplication
Work on paper. Try each question before revealing help, and explain why your method works.
Quick readiness check
What is the matrix for90° anticlockwise about the origin?
What you will learn
- Map column vectors: explain and apply the stated matrix method.
- Rotate through a stated angle: explain and apply the stated matrix method.
- Recover familiar rotations from the same rule: explain and apply the stated matrix method.
- Use exact and general-angle cases honestly: explain and apply the stated matrix method.
Matrices: build,check and explain
Worked practice
Construct each stated origin-centred rotation matrix, retaining the angle direction and exact sine/cosine values. Transform all three supplied vertices and draw both images. Explain the centre and direction; use exact square-root coordinates when requested.
| 2 | 1 |
| -1 | 3 |
| 0 | -2 |
- 90° anticlockwise
- 45° anticlockwise
Construct these matrices yourself; use sqrt(2)/2 or sqrt(3)/2 for exact square-root entries.
Record your actual working
Enter original operands and each intermediate result. Final answers will be recorded separately. 0 of 69 fields entered.
Current entries need recording.
Enter separate final answers
Enter your own answers without copying them into the working form. 0 of 21 fields entered.
Current entries need recording.
Record your complete current operands,intermediate results,matrix constructions and method.
Review the original row/column meanings, units, written dimension/method argument, and any drawn shape or geometric description. A comparison of numbers does not approve these.
What these checks can establish
- Bounded exact rational and supported simple real square-root expressions; no arbitrary code evaluation or unknown-variable repair.
- At most three rows and columns; determinant and inverse tasks use nonsingular two by two matrices. Refusing a singular inverse adds no singular-matrix syllabus requirement.
- General rotations are taught by the cosine/sine matrix. Exact 30°,45° and60° rotations supplement quarter turns; more general numerical angle proposals need explicitly reviewed trigonometric precision.
- Equivalent expressions outside the inherited finite symbolic forms need human review rather than automatic failure-as-mathematical-proof. No geometric explanation,drawn shape,official marks,mastery,specialist approval or formal assessment readiness is established by numerical agreement.
- All work operands, intermediate results and separate final answers begin blank. A correct separate answer never repairs wrong original working.
- Working records retain original row/column term operands and results; matrix construction and both inverse checks are required where requested. These fixed comparisons do not prove a written argument or a drawn transformation.
- Edits,cleared groups,withdrawal,reset,stage switches and source/session/generation/revision changes invalidate earlier results and withhold the explained reference. Direct changes to recorded fields also withdraw readiness.
- A complete incorrect attempt may study an explanation without being marked correct. Reference study is not evidence of mastery or assessment readiness.
This practice stays in the current open activity. No saved account progress, official mark or mastery result is awarded here.
Map column vectors
Represent a point (x,y) by [x;y]. For M=[a,b;c,d], its image is [ax+by;cx+dy]. The first column of M is the image of (1,0),and the second column is the image of (0,1). This gives a way to construct the matrix from its geometric description.
Map every labelled vertex of a polygon,plot the original and image points on common labelled axes,and join corresponding vertices in their original order. Correct coordinates alone do not check the axes,scale or joined shape in a drawing.
Rotate through a stated angle
An anticlockwise rotation through θ about the origin has matrix [cosθ,−sinθ;sinθ,cosθ]. For a clockwise rotation use a negative θ. The standard quarter-turn matrices follow from this formula; the formula is not restricted to multiples of 90°.
For 45° anticlockwise use [√2/2,−√2/2;√2/2,√2/2]. For 30° clockwise use [√3/2,1/2;−1/2,√3/2]. For 60° anticlockwise use [1/2,−√3/2;√3/2,1/2]. Keep these entries exact when exact coordinates are requested. Other angles can be studied with a stated precision and human review of the numerical method.
Recover familiar rotations from the same rule
At 90° anticlockwise the matrix is [0,−1;1,0],so (x,y) maps to (−y,x). At 90° clockwise it is [0,1;−1,0],so (x,y) maps to (y,−x). A 180° rotation uses [−1,0;0,−1].
A 270° anticlockwise rotation has the same matrix as 90° clockwise. State an angle and direction together;the angle alone can be ambiguous. Keep the centre at the origin for these matrix forms.
Use exact and general-angle cases honestly
Worked,Guided and Independent practice each combine a familiar rotation with a non-quarter-turn rotation using exact square roots. Application also studies a rotation with cosθ=3/5 and sinθ=4/5,where θ is in the first quadrant.
Rotations preserve the distance from the origin and the orientation of a labelled shape. Use those facts to review a drawing. The general cosine/sine formula is taught here;more general numerical angles require a stated precision and human review rather than an unsupported automatic accuracy claim.
Sources for this lesson
Pause and explain
What is the matrix for90° anticlockwise about the origin?
Worked example
Construct each stated origin-centred rotation matrix, retaining the angle direction and exact sine/cosine values. Transform all three supplied vertices and draw both images. Explain the centre and direction; use exact square-root coordinates when requested. Vertices=[2, 1; -1, 3; 0, -2] (columns x,y); transformations=90° anticlockwise, 45° anticlockwise.
Show the worked solution
- Represent each original vertex as a column vector. Keep its x-coordinate first and its y-coordinate second.
- 90° anticlockwise: the image of (1,0) is (0,1) and the image of (0,1) is (-1,0). These are the first and second matrix columns respectively.
- 45° anticlockwise: the image of (1,0) is (sqrt(2)/2,sqrt(2)/2) and the image of (0,1) is (-sqrt(2)/2,sqrt(2)/2). These are the first and second matrix columns respectively.
- For an anticlockwise angle θ,construct [[cosθ,−sinθ],[sinθ,cosθ]];a clockwise angle has a negative sine. For45° use exact √2/2 entries;for30° and60° use exact halves and √3/2. Multiply before simplifying,without rounding these exact entries.
- For every vertex,calculate both matrix-row dot products with its original coordinate column. Keep all signed terms.
- Plot and label the original and image vertices on common axes and join corresponding edges in the original order. Review the geometric description and any fixed-line or distance claim separately from the numerical comparison.
- Construct the matrix: 90° anticlockwise: [0, -1; 1, 0].
- 90° anticlockwise: vertex 1: row 1 · column 1: (0)*(2) + (-1)*(1) = -1.
- 90° anticlockwise: vertex 1: row 2 · column 1: (1)*(2) + (0)*(1) = 2.
- 90° anticlockwise: vertex 2: row 1 · column 1: (0)*(-1) + (-1)*(3) = -3.
- 90° anticlockwise: vertex 2: row 2 · column 1: (1)*(-1) + (0)*(3) = -1.
- 90° anticlockwise: vertex 3: row 1 · column 1: (0)*(0) + (-1)*(-2) = 2.
- 90° anticlockwise: vertex 3: row 2 · column 1: (1)*(0) + (0)*(-2) = 0.
- Construct the matrix: 45° anticlockwise: [sqrt(2)/2, -sqrt(2)/2; sqrt(2)/2, sqrt(2)/2].
- 45° anticlockwise: vertex 1: row 1 · column 1: (sqrt(2)/2)*(2) + (-sqrt(2)/2)*(1) = ((0)+((sqrt(2)/2)*(2)))+((-sqrt(2)/2)*(1)).
- 45° anticlockwise: vertex 1: row 2 · column 1: (sqrt(2)/2)*(2) + (sqrt(2)/2)*(1) = ((0)+((sqrt(2)/2)*(2)))+((sqrt(2)/2)*(1)).
- 45° anticlockwise: vertex 2: row 1 · column 1: (sqrt(2)/2)*(-1) + (-sqrt(2)/2)*(3) = ((0)+((sqrt(2)/2)*(-1)))+((-sqrt(2)/2)*(3)).
- 45° anticlockwise: vertex 2: row 2 · column 1: (sqrt(2)/2)*(-1) + (sqrt(2)/2)*(3) = ((0)+((sqrt(2)/2)*(-1)))+((sqrt(2)/2)*(3)).
- 45° anticlockwise: vertex 3: row 1 · column 1: (sqrt(2)/2)*(0) + (-sqrt(2)/2)*(-2) = (0)+((-sqrt(2)/2)*(-2)).
- 45° anticlockwise: vertex 3: row 2 · column 1: (sqrt(2)/2)*(0) + (sqrt(2)/2)*(-2) = (0)+((sqrt(2)/2)*(-2)).
Answer 90° anticlockwise — matrix=[0, -1; 1, 0]. 90° anticlockwise — images of vertices 1,2,3=[-1, 2; -3, -1; 2, 0]. 45° anticlockwise — matrix=[sqrt(2)/2, -sqrt(2)/2; sqrt(2)/2, sqrt(2)/2]. 45° anticlockwise — images of vertices 1,2,3=[(1/2)*sqrt(2), (3/2)*sqrt(2); (-2)*sqrt(2), (1)*sqrt(2); (1)*sqrt(2), (-1)*sqrt(2)]. Review graph placement, axes, angle/direction, centre, reflection line and scale factor. General-angle irrational entries are taught but need a separate exact-surds or reviewed numerical interface.
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Test this topic →From guided practice to a new situation
Write your answer and reasoning first. Use a hint only if you are stuck. The model solution is for self-checking; your written work is not automatically marked.
Construct each stated origin-centred rotation matrix, retaining the angle direction and exact sine/cosine values. Transform all three supplied vertices and draw both images. Explain the centre and direction; use exact square-root coordinates when requested. Vertices=[3, 1; -1, 4; 0, -2] (columns x,y); transformations=90° clockwise, 30° clockwise.
Give me a hint
Keep the original order and labels. Construct each required matrix and retain every original row–column operand or scalar operation; enter the separate final answers yourself.
Compare my reasoning
- Represent each original vertex as a column vector. Keep its x-coordinate first and its y-coordinate second.
- 90° clockwise: the image of (1,0) is (0,-1) and the image of (0,1) is (1,0). These are the first and second matrix columns respectively.
- 30° clockwise: the image of (1,0) is (sqrt(3)/2,-1/2) and the image of (0,1) is (1/2,sqrt(3)/2). These are the first and second matrix columns respectively.
- For an anticlockwise angle θ,construct [[cosθ,−sinθ],[sinθ,cosθ]];a clockwise angle has a negative sine. For45° use exact √2/2 entries;for30° and60° use exact halves and √3/2. Multiply before simplifying,without rounding these exact entries.
- For every vertex,calculate both matrix-row dot products with its original coordinate column. Keep all signed terms.
- Plot and label the original and image vertices on common axes and join corresponding edges in the original order. Review the geometric description and any fixed-line or distance claim separately from the numerical comparison.
- Construct the matrix: 90° clockwise: [0, 1; -1, 0].
- 90° clockwise: vertex 1: row 1 · column 1: (0)*(3) + (1)*(1) = 1.
- 90° clockwise: vertex 1: row 2 · column 1: (-1)*(3) + (0)*(1) = -3.
- 90° clockwise: vertex 2: row 1 · column 1: (0)*(-1) + (1)*(4) = 4.
- 90° clockwise: vertex 2: row 2 · column 1: (-1)*(-1) + (0)*(4) = 1.
- 90° clockwise: vertex 3: row 1 · column 1: (0)*(0) + (1)*(-2) = -2.
- 90° clockwise: vertex 3: row 2 · column 1: (-1)*(0) + (0)*(-2) = 0.
- Construct the matrix: 30° clockwise: [sqrt(3)/2, 1/2; -1/2, sqrt(3)/2].
- 30° clockwise: vertex 1: row 1 · column 1: (sqrt(3)/2)*(3) + (1/2)*(1) = ((0)+((sqrt(3)/2)*(3)))+(1/2).
- 30° clockwise: vertex 1: row 2 · column 1: (-1/2)*(3) + (sqrt(3)/2)*(1) = (-3/2)+((sqrt(3)/2)*(1)).
- 30° clockwise: vertex 2: row 1 · column 1: (sqrt(3)/2)*(-1) + (1/2)*(4) = ((0)+((sqrt(3)/2)*(-1)))+(2).
- 30° clockwise: vertex 2: row 2 · column 1: (-1/2)*(-1) + (sqrt(3)/2)*(4) = (1/2)+((sqrt(3)/2)*(4)).
- 30° clockwise: vertex 3: row 1 · column 1: (sqrt(3)/2)*(0) + (1/2)*(-2) = -1.
- 30° clockwise: vertex 3: row 2 · column 1: (-1/2)*(0) + (sqrt(3)/2)*(-2) = (0)+((sqrt(3)/2)*(-2)).
90° clockwise — matrix=[0, 1; -1, 0]. 90° clockwise — images of vertices 1,2,3=[1, -3; 4, 1; -2, 0]. 30° clockwise — matrix=[sqrt(3)/2, 1/2; -1/2, sqrt(3)/2]. 30° clockwise — images of vertices 1,2,3=[(1/2)+(3/2)*sqrt(3), (-3/2)+(1/2)*sqrt(3); (2)+(-1/2)*sqrt(3), (1/2)+(2)*sqrt(3); -1, (-1)*sqrt(3)]. Review graph placement, axes, angle/direction, centre, reflection line and scale factor. General-angle irrational entries are taught but need a separate exact-surds or reviewed numerical interface.
Look for these in your work
- I retain the original matrices,labels and requested order.
- My working operands,intermediate values and matrix constructions are explicit.
- My separate final answers do not replace my working.
- I review the dimensions,units and any written or geometric argument with the stated limitations.
Construct each stated origin-centred rotation matrix, retaining the angle direction and exact sine/cosine values. Transform all three supplied vertices and draw both images. Explain the centre and direction; use exact square-root coordinates when requested. Vertices=[4, 1; -1, 5; 0, -2] (columns x,y); transformations=180° rotation, 60° anticlockwise.
Give me a hint
Keep the original order and labels. Construct each required matrix and retain every original row–column operand or scalar operation; enter the separate final answers yourself.
Compare my reasoning
- Represent each original vertex as a column vector. Keep its x-coordinate first and its y-coordinate second.
- 180° rotation: the image of (1,0) is (-1,0) and the image of (0,1) is (0,-1). These are the first and second matrix columns respectively.
- 60° anticlockwise: the image of (1,0) is (1/2,sqrt(3)/2) and the image of (0,1) is (-sqrt(3)/2,1/2). These are the first and second matrix columns respectively.
- For an anticlockwise angle θ,construct [[cosθ,−sinθ],[sinθ,cosθ]];a clockwise angle has a negative sine. For45° use exact √2/2 entries;for30° and60° use exact halves and √3/2. Multiply before simplifying,without rounding these exact entries.
- For every vertex,calculate both matrix-row dot products with its original coordinate column. Keep all signed terms.
- Plot and label the original and image vertices on common axes and join corresponding edges in the original order. Review the geometric description and any fixed-line or distance claim separately from the numerical comparison.
- Construct the matrix: 180° rotation: [-1, 0; 0, -1].
- 180° rotation: vertex 1: row 1 · column 1: (-1)*(4) + (0)*(1) = -4.
- 180° rotation: vertex 1: row 2 · column 1: (0)*(4) + (-1)*(1) = -1.
- 180° rotation: vertex 2: row 1 · column 1: (-1)*(-1) + (0)*(5) = 1.
- 180° rotation: vertex 2: row 2 · column 1: (0)*(-1) + (-1)*(5) = -5.
- 180° rotation: vertex 3: row 1 · column 1: (-1)*(0) + (0)*(-2) = 0.
- 180° rotation: vertex 3: row 2 · column 1: (0)*(0) + (-1)*(-2) = 2.
- Construct the matrix: 60° anticlockwise: [1/2, -sqrt(3)/2; sqrt(3)/2, 1/2].
- 60° anticlockwise: vertex 1: row 1 · column 1: (1/2)*(4) + (-sqrt(3)/2)*(1) = (2)+((-sqrt(3)/2)*(1)).
- 60° anticlockwise: vertex 1: row 2 · column 1: (sqrt(3)/2)*(4) + (1/2)*(1) = ((0)+((sqrt(3)/2)*(4)))+(1/2).
- 60° anticlockwise: vertex 2: row 1 · column 1: (1/2)*(-1) + (-sqrt(3)/2)*(5) = (-1/2)+((-sqrt(3)/2)*(5)).
- 60° anticlockwise: vertex 2: row 2 · column 1: (sqrt(3)/2)*(-1) + (1/2)*(5) = ((0)+((sqrt(3)/2)*(-1)))+(5/2).
- 60° anticlockwise: vertex 3: row 1 · column 1: (1/2)*(0) + (-sqrt(3)/2)*(-2) = (0)+((-sqrt(3)/2)*(-2)).
- 60° anticlockwise: vertex 3: row 2 · column 1: (sqrt(3)/2)*(0) + (1/2)*(-2) = -1.
180° rotation — matrix=[-1, 0; 0, -1]. 180° rotation — images of vertices 1,2,3=[-4, -1; 1, -5; 0, 2]. 60° anticlockwise — matrix=[1/2, -sqrt(3)/2; sqrt(3)/2, 1/2]. 60° anticlockwise — images of vertices 1,2,3=[(2)+(-1/2)*sqrt(3), (1/2)+(2)*sqrt(3); (-1/2)+(-5/2)*sqrt(3), (5/2)+(-1/2)*sqrt(3); (1)*sqrt(3), -1]. Review graph placement, axes, angle/direction, centre, reflection line and scale factor. General-angle irrational entries are taught but need a separate exact-surds or reviewed numerical interface.
Look for these in your work
- I retain the original matrices,labels and requested order.
- My working operands,intermediate values and matrix constructions are explicit.
- My separate final answers do not replace my working.
- I review the dimensions,units and any written or geometric argument with the stated limitations.
A designer is placing a triangular motif on an origin-centred coordinate grid. Construct each stated origin-centred rotation matrix, retaining the angle direction and exact sine/cosine values. Transform all three supplied vertices and draw both images. Explain the centre and direction; use exact square-root coordinates when requested. Vertices=[5, 1; -1, 6; 0, -2] (columns x,y); transformations=270° anticlockwise, rotation with cosθ=3/5 and sinθ=4/5.
Give me a hint
Keep the original order and labels. Construct each required matrix and retain every original row–column operand or scalar operation; enter the separate final answers yourself.
Compare my reasoning
- Represent each original vertex as a column vector. Keep its x-coordinate first and its y-coordinate second.
- 270° anticlockwise: the image of (1,0) is (0,-1) and the image of (0,1) is (1,0). These are the first and second matrix columns respectively.
- rotation with cosθ=3/5 and sinθ=4/5: the image of (1,0) is (3/5,4/5) and the image of (0,1) is (-4/5,3/5). These are the first and second matrix columns respectively.
- For an anticlockwise angle θ,construct [[cosθ,−sinθ],[sinθ,cosθ]];a clockwise angle has a negative sine. For45° use exact √2/2 entries;for30° and60° use exact halves and √3/2. Multiply before simplifying,without rounding these exact entries.
- For every vertex,calculate both matrix-row dot products with its original coordinate column. Keep all signed terms.
- Plot and label the original and image vertices on common axes and join corresponding edges in the original order. Review the geometric description and any fixed-line or distance claim separately from the numerical comparison.
- Construct the matrix: 270° anticlockwise: [0, 1; -1, 0].
- 270° anticlockwise: vertex 1: row 1 · column 1: (0)*(5) + (1)*(1) = 1.
- 270° anticlockwise: vertex 1: row 2 · column 1: (-1)*(5) + (0)*(1) = -5.
- 270° anticlockwise: vertex 2: row 1 · column 1: (0)*(-1) + (1)*(6) = 6.
- 270° anticlockwise: vertex 2: row 2 · column 1: (-1)*(-1) + (0)*(6) = 1.
- 270° anticlockwise: vertex 3: row 1 · column 1: (0)*(0) + (1)*(-2) = -2.
- 270° anticlockwise: vertex 3: row 2 · column 1: (-1)*(0) + (0)*(-2) = 0.
- Construct the matrix: rotation with cosθ=3/5 and sinθ=4/5: [3/5, -4/5; 4/5, 3/5].
- rotation with cosθ=3/5 and sinθ=4/5: vertex 1: row 1 · column 1: (3/5)*(5) + (-4/5)*(1) = 11/5.
- rotation with cosθ=3/5 and sinθ=4/5: vertex 1: row 2 · column 1: (4/5)*(5) + (3/5)*(1) = 23/5.
- rotation with cosθ=3/5 and sinθ=4/5: vertex 2: row 1 · column 1: (3/5)*(-1) + (-4/5)*(6) = -27/5.
- rotation with cosθ=3/5 and sinθ=4/5: vertex 2: row 2 · column 1: (4/5)*(-1) + (3/5)*(6) = 14/5.
- rotation with cosθ=3/5 and sinθ=4/5: vertex 3: row 1 · column 1: (3/5)*(0) + (-4/5)*(-2) = 8/5.
- rotation with cosθ=3/5 and sinθ=4/5: vertex 3: row 2 · column 1: (4/5)*(0) + (3/5)*(-2) = -6/5.
270° anticlockwise — matrix=[0, 1; -1, 0]. 270° anticlockwise — images of vertices 1,2,3=[1, -5; 6, 1; -2, 0]. rotation with cosθ=3/5 and sinθ=4/5 — matrix=[3/5, -4/5; 4/5, 3/5]. rotation with cosθ=3/5 and sinθ=4/5 — images of vertices 1,2,3=[11/5, 23/5; -27/5, 14/5; 8/5, -6/5]. Review graph placement, axes, angle/direction, centre, reflection line and scale factor. General-angle irrational entries are taught but need a separate exact-surds or reviewed numerical interface.
Look for these in your work
- I retain the original matrices,labels and requested order.
- My working operands,intermediate values and matrix constructions are explicit.
- My separate final answers do not replace my working.
- I review the dimensions,units and any written or geometric argument with the stated limitations.
Common mistakes
- Changing the sign of cosine instead of using the correct sine signs.
- Calling a clockwise turn anticlockwise.
- Using rounded coordinates when exact surds are requested.
- Claiming that the finite practice angles are all rotations allowed by the syllabus.
What can you explain now?
What is the matrix for90° anticlockwise about the origin?
Compare with the explanation
[0,−1;1,0].
The first basis vector maps to(0,1) and the second to(−1,0).
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Make it stick
Reconstruct the method from the original givens,justify every matrix order,retain all signed entries,and explain the result in its original labels,units or geometry. A fixed numerical comparison does not establish a written argument,mastery,specialist approval or formal assessment readiness.
If you needed the solution, close it and solve the problem again from a blank page. A correct answer is stronger when you can explain the reason for each step.