Question

Use the law of cosines to find the value of costheta

Answer 1

I already tried using
a^1+b^2-2abcos(c)=c^2
and I tried using
cos(a)=(b^2+c^2-a^2)/(2ab)

Answer 2

on your above image where are a,b and c ?

Answer 3

hmm, in the intial question they arent labled but I am going to assume here