Answer
$-0.5(\cos(x+y)-\cos(x-y))$
Work Step by Step
From what we learned $\sin x\sin y=-0.5(\cos(x+y)-\cos(x-y))$
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.