Question

prove that a3 cos(b-c)=3abc​

Answer 1

Originally Answered: How do I prove this trigonometric identity: a ^3cos(B-C) + b^3cos(C-A) + c^3cos(A-B) = 3abc ?

You can find a proof at GeeksNetworks: Properties of Triangles (This question is based on Properties of Triangles), Prove that in a triangle ABC, a^3 . cos(B-C) + b^3 . cos(C-A) + c^3 . cos(A-B) = 3abc.