1.

Prove that:2sin75°sin15° = 1/2

Answer»

L.H.S

= 2sin75°sin15°

= 2sin(45° + 30°)sin(45° - 30°)

= cos(45° - 30° - 45° - 30°) - (cos45° + 30° + 45° - 30°)

= cos(-60°) - cos90°

= cos60° - 0

\(\frac{1}{2}\)



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