Question

prove that sin 780 Sin 480+
Cos 120 Sin 30 =1/
2​

Answer 1

Answer:

L.H.S=R.H.S.

Step-by-step explanation:

L.H.S:-

= sin 780 sin 480 + cos 120 sin 30

= sin ( 8 × 90 ° + 60° ) sin ( 5 × 90° + 30° ) + cos ( 1× 90° + 30° ) sin 30°

= sin 60° cos 30° + sin 30° sin 30°

=. √3/2 × √3/2 + 1/2 × 1/2

= (√3)²/4 + 1/4

= 3/4 + 1/4

=. 3+1/4

= 4/4

=. 1

hence proved