Question

show that sin 3x = 3 sin x - 4 sin³ x​

Answer 1

Answer:

hope it helps...................

Answer 2

Step-by-step explanation:

Using sin(a + b) = sin a cos b + cos a sin b

sin(3x) = sin(2x + x) = sin 2x cos x + cos 2x sin x

Using cos(2a) = 1 - 2 sin^2 a

= 2 sin x cos x cos x + (1 - 2sin^2 x) sin x

Using sin^2 a + cos^2 a = 1 ; cos^2 a = 1 - sin^2 a

= 2 sin x(1 - sin^2 x) + sin x - 2 sin^3 x

= 3 sin x - 4 sin^3 x

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