Guest: what are the law of cosines? and how do we solve it?
I know the law of cosines as the cosine rule.
We use the cosine rule to find an angle in a triangle if we have three sides.
or
We can use it to find the side or a triangle if we have the other 2 sides and the opposite angle.
Have a look here.
http://www.mathsisfun.com/algebra/trig-cosine-law.html
Have fun.
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