Question

Prove That , Cos2x = Cos²x - Sin²x​

Answer 1

$\underline{ \large{ \bold{Identity :- \: }}}$

$\to\bold{Cos( \: A \: + \: B \: )} = \bold{Cos \: A \: \: \times Cos \: B \: \: - \: Sin \: A \: \: \times \: Sin \: B \: \: }$

$\large{\underline{ \bold{ To \: Prove :- \: }}}$

$\to \bold{Cos2x \: = \bold{ {Cos}^{2}x \: } - \: {Sin}^{2}x}$

$\large{ \underline{ \bold{Proof :- \: }}}$

$\to\bold{Cos2x \: } \\ \to\bold{Cos( \: x \: + \: x \: )} \\ \to\bold{Cosx \: \times Cosx \: - \: Sinx \: \times \: Sinx } \\ \to\bold{ {Cos}^{2}x \: - \: {Sin}^{2}x }$

Answer 2

Answer:

refer to the attachment