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Question
If A =30o, then prove that :
sin 3A = 3 sin A - 4 sin3A.
Solution
Given A = 30°
sin 3A = sin 3(30°)
= sin 90°
=1
3 sin A – 4 sin3A = 3 sin 30° – 4 sin330°
=`3(1/2) – 4(1/2)^3`
= `(3)/(2) – (1)/(2)`
= 1
∴ sin 3A = 3 sin A – 4 sin3A
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