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 Notes: Side a is opposite angle A, side b opposite angle B and side c opposite angle C Side AB is the hypotenuse. For angle A side BC is the opposite and AC the adjacent   SOHCAHTOA SOH... Sine = Opposite / Hypotenuse ...CAH... Cosine = Adjacent / Hypotenuse ...TOA Tangent = Opposite / Adjacent

MATH STUDIES

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Geometry and Trigonometry

Right angled Trigonometry

1. Pythagoras's Theorem : (The square on the hypotenuse is equal to the sum of the squares on the other two sides)

a2+b2=c2  or  AB2 = AC2 + BC2

2. SOHCAHTOA

3. Area of triangle ABC

Example:

Given AB = 8cm and BC = 5cm  Find

1. AC

2. Angle C

3. Area of triangle ABC

Working:

1. From Pythagoras we know AB2 = AC2 + BC2

Hence  82 = AC2 + 52

AC2 = 82 - 52

units. This is the exact answer or 6.24 units to 3 significant figures

2. Area of triangle ABC

Note: Not all triangles have a right angle, for non-right angled triangles we have other rules

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