Question

The cos.sin(90- theta) question

Answer 1

Answer:

Answer is in the attachment

hope it helps you

Answer 2

$\huge \bold \color{teal} \mathfrak{Answer}$

$let \: theta = \alpha$

$\cos( \alpha ) \sin(90 - \alpha ) + \sin( \alpha ) \cos(90 - \alpha )$

$since \: \sin(90 - \alpha ) = \cos( \alpha ) \\ and \: \cos(90 - \alpha ) = \sin( \alpha )$

$\cos( \alpha ) \cos( \alpha ) + \sin( \alpha ) \sin( \alpha )$

$\cos {}^{2} ( \alpha ) + \sin {}^{2} ( \alpha ) = \huge \bold \color{green} {1}$

Hope it helps...