Question

Cos 48 x Cos 42° - Sin 48 x Sin 42°

Answer 1

cos48 cos42 - sin48 sin42

= cos(90-42) cos(90-48) - sin48 sin42

=sin42 sin48 - sin48 sin42 {cos(90- 0) = sin0}

= 0. ans

Answer 2

Step-by-step explanation:

cos48×cos42°-sin48×sin42°

={cos (90-42) × cos(90-48)}-sin48×sin42°

=(sin42×sin48) -(sin 48×sin42)

{cos90-theta=sin theta }

=0