Answer
See the steps.
Work Step by Step
$\sin{(\dfrac{3\pi}{2}-x)} = \sin{\dfrac{3\pi}{2}} \cos{x} - \cos{\dfrac{3\pi}{2}} \sin{x}$
$\sin{(\dfrac{3\pi}{2}-x)} = -1 \times \cos{x} - 0 \times \sin{x} = - \cos{x}$
You can help us out by revising, improving and updating this answer.
Update this answerAfter you claim an answer you’ll have 24 hours to send in a draft. An editor will review the submission and either publish your submission or provide feedback.