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Question
If A = 30°;
show that:
sin 3 A = 4 sin A sin (60° - A) sin (60° + A)
Solution
Given that A = 30°
LHS = sin 3 A
= sin 3(30°)
= sin 90°
=1
RHS = 4 sin A sin (60° – A) sin (60° + A)
= 4 sin 30° sin ( 60° – 30°) sin (60° + 30°)
= `4(1/2)(1/2)(1)`
= 1
LHS = RHS
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