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LearnCambridge4024Current syllabusPaper 2 · CalculatorTrigonometry

Paper 2 · Module

Trigonometry

4 subtopics≈ 135 min in total

Start the module: Pythagoras' theorem Open graphing calculator

Pythagoras' theorem
In a right-angled triangle, the square on the hypotenuse equals the sum of the squares on the other two sides: $a^2+b^2=c^2$ . Add the squares to find the hypotenuse; subtract to find a shorter side.
≈ 25 min
Right-angled trigonometry
Label the sides opposite, adjacent and hypotenuse relative to the angle. Then SOHCAHTOA tells you which ratio links the two sides you know (or want). Use the ratio to find a side, or the inverse function to find an angle.
≈ 35 min
Sine rule, cosine rule and area
For triangles without a right angle: use the sine rule when you know a side and its opposite angle, and the cosine rule when you know two sides and the angle between them, or all three sides. The area is $\tfrac12ab\sin C$ .
≈ 40 min
Trigonometry in three dimensions
Every 3D problem is a chain of 2D right-angled triangles. Find a triangle on the base first (often a diagonal), then stand a vertical triangle on it. The angle between a line and a plane is the angle between the line and its shadow on the plane.
≈ 35 min