Q8 of 90 Page 9

Take L.H.S:





cos α cos β


Multiplying & Dividing by 2:



{2 cos A cos B = cos (A + B) + cos (A – B)}







We know,







More from this chapter

All 90 →
6

Show that

i. sin A sin (B – C) + sin B sin (C – A) + sin C sin (A – B) = 0


ii. sin (B – C) cos (A – D) + sin (C – A) cos(B – D) + sin(A – B) cos(C – D) = 0

 7

Prove that:

 1

Express each of the following as the product of sines and cosines:

i. sin 12x + sin 4x


ii. sin 5x – sin x


iii. cos 12x + cos 8x


iv. sin 2x + cos 4x

 2

Prove that :

sin 38° + sin 22°= sin 82°