Sine&Cosine Rule

We can use trigonometry to work out a missing side or angle in a right angled triangle.

for example:

if a right angled triangle's opposite and adjacent sides are of the same length then the missing angle must be 45o

Often in real life situations th triangle is not right angled.

When this is the case we can use the sine and cosine rules.

The sine rule

the rule is:

$a/sinA = b/sinB = c/sinC$

this rule allows us to work out any missing side or angle provided we know some of the lengths and angles in the triangle.

So suppose we know that angle A in the triangle above is 45o, that angle B is 30o and that the length b is 2cm.

Can you work out the remaining angle C and the lengths a and c?

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