Question

Prove that:-
cosAsin(B-C) + cosBsin(C-A) + cosCsin(A-B) =0

Answer 1

Help

Answer 2

expand
sin (x-y) = sin x cos y - cos x sin y

all 3 sin terms

Answer 3

oh wait

Answer 4

if i am not wrong , everything will cancel out

Answer 5

yup

Answer 6

cool :)

Answer 7

thank you

Answer 8

welcome ^_^

Answer 9

hehe , i was doing cos c + cos d and all of that

Answer 10

Infact you can do that..

Answer 11

That is simpler to apply here.

Answer 12

You must know that:

\[2\cos(x)\sin(y) = \sin(x+y) - \sin(x-y)\]

Answer 13

yeah i know :)

Answer 14

yes yes we can apply that , also cool:)

Answer 15

Multiply and divide by 2 first, and then apply the formula there, the terms will easily cancel out...

Answer 16

always good to know alternate methods :)