Question

Reduce the following trigonometric expression.
Expression=
$\cos(x - \frac{\pi}{2} )$


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Answer 1

$\therefore cos\big(x-\frac{\pi}{2}\big)$

$=cos\big[-\big(\frac{\pi}{2}-x\big)\big]$

$=cos\big(\frac{\pi}{2}-x\big),\quad since\:cos(-\theta)=cos\theta$

$=sinx$