Question

Cos inverse A + Cos inverse b + Cos inverse z = 180 then prove that in a square + b square + c square + 2 ABC equal one

Answer 1

let's cosinverse a= x
then a= cos x
thus b = cos y
and c = cos z
then putting value of a; b;c in equation and we can prove it a2 +b2 +c2 =1_2abc
and you can get ans
if you can not get ans please comment
$(cos {)}^{2} b = 1 - (sin) {}^{2} b$