Q5 of 90 Page 9

Prove that:

Take L.H.S



Multiplying & Dividing by 2:



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





{∵ cos (-A) = cos A}




Multiplying & Dividing by 2:



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




{∵ sin (-A) = - sin A}



{∵ sin (180° - A) = sin A}





= R.H.S


Hence Proved


More from this chapter

All 90 →
5

Prove that:

tan 20° tan 40° tan 60° tan 80° = 3

 5

Prove that:

tan 20° tan 30° tan 40° tan 80° = 1

 5

Prove that:

 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