# trigonometry

trig rules including the sine and cosine rules

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• Created by: pippa
• Created on: 29-05-12 13:42

## right angled triangles

Rememeber:

for all right angled triangles you must use soh cah toa

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## soh rule

soh is opposite over hypotensue = sin

if you are trying to find sin rememeber to use the shift button and then the sin button to gain the angle

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## cah rule

cos is adjacent over hypotunese = cos

if you are trying to get the angle rememeber to use the shift button then the cos button on your calculator

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## toa rule

tan is opposite over adjcent = tan

if you are trying to find the angle press shift then the tan button on your calculator

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## the sine rule

use if :

you have 2 sides and 1 angle and trying to find an angle

you have 1 side and 2 angles and trying to find a side

the side opposite the angle is a matching pair

example:

a over sinx = b over siny

subsitute in the numbers

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## the cosine rule

you will always have 3 sides and 1 angle when using the cosine rule but one of them will be your unknown

the equation to use is:

a(squared) = b(squared) + c(squared) - 2bccosA

the a and cosA must be opposite to each other.

sub in the numbers and if needed rearrange the equation.

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