GCSE Maths

Trigonometry Summary

The longest side of a right-angled triangle is the hypotenuse

The other two sides are opposite or adjacent to a chosen angle.

Pythagoras's Theorem is that the side lengths always relate thus:
hypotenuse² = opposite² + adjacent²

Ratios between sides are normally called sin, cos and tan.

The word soh-cah-toa can help you learn them!

soh means sin = o÷h
cah means cos = a÷h
toa means tan = o÷a

Knowing the lengths of sides, we can find a sin, cos or tan ratio. From this angles can be found using inverse-sin (or inverse-cos, or inverse-tan) on scientific calculators.

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