The Cosine Rule Part 2 - GI Online Academy

The cosine rule
We can use the cosine formula to find the length of a side or size of an angle.
For a triangle with sides a,b and c and angles A, B and C the cosine rule can be written as:
a2 = b2 + c2 - 2bc cos A
or
b2 = a2 + c2 - 2ac cos B
or
c2 = a2 + b2 - 2ab cos C
These formulae can be rearranged to give :
cos A = b to the power 2 + c to the power 2 - a to the power 2 over 2 b c
cos B = a to the power 2 + c to the power 2 - b to the power 2 divided by 2 a c
cos C = a to the power 2 + b to the power 2 - c to the power 2