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A Level · Cambridge (CIE) · 9709

Sketch trigonometric graphs and track their transformations

Use periods, ranges, key points and tangent asymptotes to sketch graphs in degrees or radians.

Section 1.5 · Trigonometry

Pure Mathematics 1 · Trigonometry · 1.5 / 3.3

Pure Mathematics 1 (Paper 1) · AS & A Level Mathematics 9709, 2026–2027. State angle units and find every solution in the supplied interval; general forms of solution are not required in section 1.5. Written practice is self-checked. This sine, cosine and tangent graph foundation also supports Pure Mathematics 3 (Paper 3, A Level), section 3.3, alongside the shared reciprocal-function lessons.

Before you begin

  • Convert degrees and radians.
  • Understand function graph transformations and an excluded input.

Work on paper. Try each question before revealing help, and explain why your method works.

Quick readiness check

What is the radian period of sin x?

What you will learn

  • Sketch and use sine, cosine and tangent for angles of any size.
  • Apply vertical scaling, horizontal scaling, shifts and reflections to trigonometric graphs.
Changing period, direction and midline-10120π/2π3π/22πyx (radians)Dashed: y = cos xSolid: y = 1 − cos 2x
The dashed grey curve is y = cos x, with range [−1, 1] and period 2π. The solid blue curve is y = 1 − cos 2x, with range [0, 2] and period π. It has minima at x = 0, π, 2π and maxima at π/2, 3π/2. The horizontal axis measures radians; vertical values measure the function output. The transformed curve completes two periods in the displayed interval 0 ≤ x ≤ 2π.

Build a sketch from landmarks and repetition

Sine and cosine are defined for every real angle, have range −1 ≤ y ≤ 1 and repeat after 360° or 2π radians. In one radian period, sin x takes values 0, 1, 0, −1, 0 at x = 0, π/2, π, 3π/2, 2π. Cosine takes 1, 0, −1, 0, 1 at those inputs. Repeat the pattern for negative inputs or further turns; label the horizontal axis with its angle unit.

Tangent has period 180° or π radians and takes every real output. It is undefined when cos x = 0: for example at π/2 and 3π/2. These are vertical asymptotes, not points to join across. Within −π/2 < x < π/2, tan x increases through (0, 0) and becomes unbounded towards either asymptote. Tangent does not have the bounded range or amplitude of sine and cosine.

Transform the input before applying the output change

For y = a sin(bx) with b ≠ 0, the amplitude is |a| and the radian period is 2π/|b|. A vertical shift changes the midline but not the period. For y = 1 − cos 2x, first halve the cosine period to π, then reflect vertically and shift up 1. Its range is 0 ≤ y ≤ 2, with minima at 0, π, 2π and maxima at π/2, 3π/2 in the displayed interval.

For y = tan(x + π/4), shift the tangent graph left π/4. On −π/2 < x < π/2 it has a zero at −π/4 and an asymptote at π/4, with separate branches on either side. A shift inside brackets has the opposite direction from its written sign. Mark asymptotes before plotting and never draw a continuous curve through an excluded input.

Pause and explain

What is the range of y = 1 − cos 2x?

Put the idea to work

Worked example

Describe and sketch y = 1 − cos 2x for 0 ≤ x ≤ 2π.

Show the worked solution
  1. The input factor 2 halves the cosine period from 2π to π.
  2. The negative sign reflects the output and +1 shifts its midline to y = 1, so its range is [0, 2].
  3. Plot minima at (0, 0), (π, 0), (2π, 0) and maxima at (π/2, 2), (3π/2, 2), joining smoothly.

Answer Period π; range 0 ≤ y ≤ 2; minima at x = 0, π, 2π and maxima at x = π/2, 3π/2.

Try a topic test

Choose Easy, Normal or Difficult. Save your answers and open worked review after finishing.

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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.

1 · Guided

For y = 3 sin x on 0 ≤ x ≤ 2π, give five quarter-period points, its amplitude and period.

Give me a hint

Scale the standard sine outputs by 3 while retaining the original input positions.

Compare my reasoning
  1. Use inputs 0, π/2, π, 3π/2 and 2π with sine outputs 0, 1, 0, −1 and 0.
  2. Multiply each output by 3 to get (0, 0), (π/2, 3), (π, 0), (3π/2, −3), (2π, 0).
  3. The greatest distance from the midline is 3 and the pattern repeats after 2π.

Points (0, 0), (π/2, 3), (π, 0), (3π/2, −3), (2π, 0); amplitude 3; period 2π.

Look for these in your work

  • Scale outputs without changing the input positions.
  • Distinguish amplitude from period.
2 · Independent

Describe the range, period and turning points of y = 1 − cos 2x on 0 ≤ x ≤ 2π.

Give me a hint

First locate where cos 2x is 1 or −1; the reflection reverses which is a maximum.

Compare my reasoning
  1. The period is 2π/2 = π and the range is [0, 2].
  2. cos 2x = 1 at x = 0, π, 2π, giving minimum output 0.
  3. cos 2x = −1 at x = π/2, 3π/2, giving maximum output 2.

Period π; range [0, 2]; minima (0, 0), (π, 0), (2π, 0); maxima (π/2, 2), (3π/2, 2).

Look for these in your work

  • Account for the horizontal factor and both output transformations.
  • Identify every extremum in the stated interval.
3 · Transfer

For y = tan(x + π/4) on −π/2 < x < π/2, identify its zero, vertical asymptote and period. Explain how to draw its branches.

Give me a hint

Shift the standard tangent input landmarks left π/4.

Compare my reasoning
  1. The permitted zero occurs when x + π/4 = 0, so x = −π/4.
  2. The only asymptote in this interval occurs at x + π/4 = π/2, so x = π/4.
  3. The period remains π; sketch two increasing branches separated at π/4 and do not assign a value there.

Zero x = −π/4; asymptote x = π/4; period π; separate increasing branches.

Look for these in your work

  • Move input landmarks in the correct direction.
  • Represent the excluded asymptote instead of joining across it.

Common mistakes

  • Label whether the input axis is in degrees or radians.
  • A horizontal input factor changes period, rather than amplitude.
  • Tangent is undefined at its vertical asymptotes; do not connect the branches across them.
Recall without your notes

What can you explain now?

Give the amplitude and period of y = 3 sin x using radians.

Compare with the explanation

Amplitude 3; period 2π.

The output factor scales the vertical values only; the unscaled input keeps the sine period.

After trying it yourself, choose your next review. This is your self-assessment.

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Make it stick

Sketch one period of sine, cosine and tangent from memory. Explain how an output multiplier, input multiplier and input shift affect each sketch.

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.

Keep learning Mathematics

Course scope and assessment

312 sequenced lessons provide 936 guided, independent and application problems covering the 160 objectives in sections 1.1–1.8, 2.1–2.6, 3.1–3.9, 4.1–4.5, 5.1–5.5 and 6.1–6.5. The map lists all 38 sections across six alternative components; all eight Pure Mathematics 1 sections and all six Pure Mathematics 2 sections, from Paper 2 Algebra through Numerical solution of equations, currently have full teaching sequences. Paper 3 Algebra, section 3.1, links the six shared foundation lessons plus six lessons on partial fractions and rational binomial expansions; Paper 3 logarithms, trigonometry and numerical equations use the shared lessons, with the Paper 1 graph foundation linked into trigonometry. Paper 3 differentiation combines the shared methods with its inverse-tangent derivative lesson. Paper 3 Integration links four shared standard and identity lessons plus seven advanced lessons, covering all six section 3.5 requirements. Eight Vectors lessons cover all six section 3.7 requirements, with 2D and 3D line and solid applications. Nine Differential equations lessons cover all four section 3.8 requirements, including Paper 3 integration techniques, initial conditions, equilibrium solutions and conditional model interpretations. Eleven Complex numbers lessons cover all eight section 3.9 requirements, with seven Argand diagrams and explicit argument and boundary checks. All nine Pure Mathematics 3 sections now have teaching linked to every mapped requirement. Nine Forces and equilibrium lessons cover all seven section 4.1 requirements, with six force diagrams, signed incline-friction intervals, reaction-dependent pull and push limits and separate-body third-law checks. Nine Kinematics lessons cover the four official section 4.2 requirements, with the graph requirement mapped to three relationships. Six motion diagrams support directed quantities, graph slopes and signed areas, Paper 1 time-calculus methods, reversal distances, constant-acceleration stages and shared-clock particle meetings. Six Momentum lessons cover both section 4.3 requirements, including signed system totals, conservation assumptions, outgoing velocities, coalescence, unknown masses and successive impacts. Four diagrams show system momentum through the stipulated events, and supplied kinetic-energy checks distinguish conservation of momentum from changes in kinetic energy. Twelve Newton’s laws lessons cover all four section 4.4 requirements, with vertical support and release stages, rough horizontal and incline motion, inferred parameters, hanging and surface pulley systems, rigid tow-bar thrust and slack-string transitions. Seven force diagrams support the separate-particle balances. Nine Energy, work and power lessons cover all five section 4.5 requirements, with angle-dependent work, kinetic and reference potential energy, signed net-work balances, smooth curved slides, rough and driven slopes, ideal connected-system energy and instantaneous power on hills. Five diagrams distinguish the energy inputs, losses and valid positive-speed force model. All five Mechanics sections now have teaching and staged practice linked to their mapped requirements. Thirteen Representation of data lessons cover all five section 5.1 requirements, including choice and limitations of displays, ordered and back-to-back stems, raw summaries and box plots, unequal-width density histograms, cumulative-frequency interpolation, descriptive moment calculations, grouped estimates, coding, combining two datasets and correcting totals. Six accessible diagrams retain repeated observations and distinguish numerical spread, frequency area and estimated readings. Ten Permutations and combinations lessons cover both official section 5.2 requirements, with selection and ordered roles, repeated objects, adjacency blocks, non-adjacency gaps, leading-zero cases, labelled multi-row seating and mixed restrictions. Six accessible diagrams show outcome trees, ordered versus unordered choices, repeated copies, blocks, gaps and distinct row seats. Eleven Probability lessons cover all four section 5.3 requirements, with equiprobable elementary outcomes, selection-based probabilities, complements and disjoint regions, independence tests, restricted sample spaces, two-way tables, replacement and removal trees, reversed conditions and unknown parameters. Seven accessible diagrams show dice outcomes, random subsets, event regions, a conditioned grid, a count table and two probability trees. Twelve Discrete random variables lessons cover all three official section 5.4 requirements, with complete probability tables, moment and parameter checks, binomial assumptions, exact probabilities and moments, geometric first-success probabilities, tails, expectation and integer reliability thresholds. Six accessible diagrams distinguish outcome grouping, weighted moments, fixed trials, discrete probability bars, waiting conventions and integer tail deadlines. Twelve Normal distribution lessons cover all three official section 5.5 requirements, with continuous-area interpretation, MF19 cumulative tables, full standardisation, tail and interval regions, conditional probabilities, percentiles, one- and two-parameter inference, binomial suitability, continuity corrections and approximate integer thresholds. Seven accessible diagrams show model areas, table reading, aligned scales, intervals, quantiles, matched binomial and normal shapes and whole integer cells. All five Statistics 1 sections now have teaching and staged practice linked to their mapped requirements. Fourteen Poisson distribution lessons cover all five official section 6.1 requirements, with homogeneous event-count assumptions, exposure scaling, exact masses and tails, conditional count events, moments, parameter inference, probability duration targets, disjoint and overlapping windows, rare-count binomial approximations, matched normal approximations and continuity corrections. Nine accessible diagrams show event exposures, unit conversions, discrete bars, complete tail complements, population moments, shared windows, approximate count models and integer cells. Exact checks distinguish approximate and exact close-target decisions. Fourteen Linear combinations lessons cover the six listed results in official section 6.2, with affine moments, signed scales and constant cases, expectation without independence, independent squared variance contributions, fixed and random fees, independent copies versus reused values, affine normal events, independent normal sums and differences, weighted and conditional areas, coefficient inference, exact independent Poisson sums and overlapping exposure limits. Nine accessible diagrams distinguish scale changes, variance contributions, component costs, copy mechanisms, aligned normal scales, summed areas, Poisson count pairs and unsupported distribution claims. Fourteen Continuous random variables lessons cover both official section 6.3 requirements, with density validity and units, support-aware intervals, complements and conditional regions, first and second moments, percentiles by direct density areas, symmetry checks, parameter inference, infinite-support power and exponential integrals, divergent-moment limits and combined applications. Nine accessible diagrams distinguish density height from probability, normalisation, negative-density failures, central and conditional areas, mean versus median, percentile locations and partial infinite tails. Explicit cumulative distribution function knowledge is not required. Eighteen Sampling and estimation lessons cover all eight official section 6.4 requirements, with population and frame definitions, random-number selection, sampling-quality limits, independent sample-mean moments, normal means, CLT conditions, SE scaling, raw, summarised and coded unbiased estimates, known-variance and large-sample mean intervals, repeated-sampling interpretation, precision planning, proportion intervals, sparse-outcome limits and contextual applications. Ten accessible diagrams distinguish selection frames, number rejection, repeated sample means, population versus mean density, CLT models, variance divisors, interval targets, illustrative coverage, integer size checks and proportion margins. Eighteen Hypothesis tests lessons cover all five official section 6.5 requirements, with pre-specified alternatives, inclusive count tails, explicit equal-tail conventions, integer critical regions and actual significance, exposure-aware Poisson tests, continuity-corrected count approximations, normal and large-sample mean tests, confidence-interval connections, error classifications, fixed-region binomial, Poisson and normal error probabilities and sample-size power comparisons. Nine accessible diagrams show the testing procedure, exact count regions, unequal Poisson tails, discrete significance jumps, corrected count boundaries, matching mean intervals and alternative error distributions. All shared lessons are counted once in the course total. All 38 sections now link teaching and practice. Eight earlier overview lessons remain available, but do not count as full section coverage. This is a content-availability measure, not full programme completion or exam readiness. Written practice is self-checked, not officially marked. Check the 2028–2030 syllabus separately if sitting an examination from 2028; this teaching map uses 2026–2027 requirements.

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