GCSE Maths (Edexcel)

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The Trigonometric Functions

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Geometry and Measures Mensuration and Calculation

The Trigonometric Functions

3:47 Introduction to Trigonometry
Spec R12 G20
Previous Labelling Right-Angled Triangles Next Pythagoras' Theorem
  • Trigonometric functions (sine, cosine, tangent) relate the sides of a right angled triangle to the angle theta.
  • The hypotenuse is always opposite the right angle.
  • The side opposite the labeled angle theta is called the opposite.
  • The side next to or adjacent to the labeled angle theta is called the adjacent.
  • The ratios between the sides of the triangle depend on the angle theta.
  • The trigonometric functions can be found by taking ratios of two of the three sides.
  • Sine theta = opposite/hypotenuse.
  • Cosine theta = adjacent/hypotenuse.
  • Tangent theta = opposite/adjacent.
  • Calculation triangles can be used to remember these ratios.
  • Mnemonic SO CA TOA can be used to remember the triangles.

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