MathsYears 12–13Trigonometry

Trigonometric identities and equations

Use tan = sin/cos and sin^2 + cos^2 = 1 to prove identities and solve trigonometric equations

What you'll learn

  1. 1

    Imagine a right-angled triangle drawn inside a circle — the sine and cosine of an angle are just the coordinates of a point on the circle's edge! 🎯

  2. 2

    What is sin²θ + cos²θ always equal to?

  3. 3

    Let's solve sinθ = 0.5 for θ between 0° and 360°.

  4. 4

    Use the protractor to find the angle whose sine is 0.5 — drag the arm!

  5. 5

    If cosθ = 0.5, what is one solution between 0° and 360°?

  6. 6

    Let's solve 2cos²θ - 1 = 0 for θ from 0° to 360°.

  7. 7

    How many solutions does sinθ = 0 have between 0° and 360°?

Practise Trigonometric identities and equations with Whizlo

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