Question
Wed June 08, 2011 By: Ayush Sagar

Prove that

Expert Reply
Wed June 08, 2011
L.H.S. = 4 sinA sin (60° + A) . sin (60° ? A)
= 4sinA{sin (60° + A) . sin (60° ? A)}
= 4sinA {sin260? sin2A}
= 4sinA{3/4?sin2A} = 3sinA ?4sin3A = sin3A = R.H.S
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