prove that cos 4x = 1 - 8 sin2x + 8sin4x - Maths - Trigonometric Functions

Question

prove that cos 4x = 1 - 8 sin2x + 8sin
4x

Ajinder Singh · Answer

cos4x = cos2(2x)
=(1- 2 sin2 2x )
= (1- 2(2 sinx cosx )2 )
= 1- 8 sin2x cos2 x )
= 1- 8 sin2x (1- sin2 x)
= 1- 8 sin2 x + 8 sin4 x proved
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prove that cos 4x = 1 - 8 sin2x + 8sin 4x

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