SOLUTION: If A, B, C are angles of a triangle, prove that cosA + cosB + cosC = 4sin(A/2)sin(B/2)sin(C/2)

Question 1131925: If A, B, C are angles of a triangle, prove that
cosA + cosB + cosC = 4sin(A/2)sin(B/2)sin(C/2)
Answer by MathLover1(20850) (Show Source): You can put this solution on YOUR website!
As , and are angles of a triangle, we have
and

Hence

=.......since

=...since

=......factor

= ........from =>

=

=

=

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