Question

prove this.... imp.... cos 2 A = cos ^2 A - sin ^2 A.... no spams plz.... take it seriously n answer ​

Answer 1

Answer:

$\cos(2a) = \cos(a + a) \\ = \: \cos(a) \cos(a) - \sin(a) \sin(a) \\ = { \cos(a) }^{2} - { \sin(a) }^{2}$

Answer 2

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