Question

what is the answer of : cos(a+b)×cos(a-b)​

Answer 1

Solution ==》》

$\cos(a + b) \\ \\ \cos(a) \times \cos(b) - \sin(a) \times \sin(b) \\ \\ \cos(a - b) \\ \\ \cos(a) \times \cos(b) + \sin(a) \times \sin(b)$

$\huge \bold{we \: know \: that}$

$(a - b)(a + b) = a {}^{2} - b {}^{2}$

$\cos(a) \cos(b)$

$\sin(a) \sin(b)$

$( { \cos(a) \cos(b) }^{2} ) - ( { \sin(a) \sin(b) }^{2} )$

Answer 2

Hey mate...

Ur answer is in the attachment....