Question

In the following questions, simplify the given formulae:

2.sin50°cos 40° - cos50°sin 40°

3.cos75°cos 15° - sin75°sin 15°​

Answer 1

Explanation:

sin(A − B) = sin A cos B − cos A sin B

sin50°cos 40° - cos50°sin 40°

= sin(50-40)°

=sin10°

cos(A + B) = cos A cos B − sin A sin B

cos75°cos 15° - sin75°sin 15°

= cos(75+15)° = cos90° = 0