Solution :
The formula of 2 cos A cos B is cos (A + B) + cos (A – B).
Example : Solve : 2 cos 75 cos 15.
Solution : We have,
2 cos 75 cos 15 = cos (75 + 15) + cos (75 – 15)
= cos 90 + cos 60
= 0 + \(1\over 2\)
= \(1\over 2\)
The formula of 2 cos A cos B is cos (A + B) + cos (A – B).
Example : Solve : 2 cos 75 cos 15.
Solution : We have,
2 cos 75 cos 15 = cos (75 + 15) + cos (75 – 15)
= cos 90 + cos 60
= 0 + \(1\over 2\)
= \(1\over 2\)