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