Question

pT Sin 780 sin480+cos120cos60=1/2

Answer 1

sin780. sin480 + cos120.sin150 
=sin(8 x 90+60).sin(5 x90+30) + cos(2 x90 -60).sin(2 x90 +30) 
=sin60.cos30 + cos60.(-sin30) 
=sin60.cos30 - cos60.sin30 
=sin(60 -30) 
=sin30 
=1/2

Answers

Identities Used: sin x = sin (180° - x) cos x = -cos (180° - x) sin x = cos (90° - x) cos (x + y) = cos x cos y - sin x sin y co