<p>The question implies that it requires the use of double-angle identities, but I was unable to get anywhere with manipulating the formula.</p>
<p>Can you double check that you wrote the question correctly?</p>
<p>The question implies that it requires the use of double-angle identities, but I was unable to get anywhere with manipulating the formula.</p>
<p>Can you double check that you wrote the question correctly?</p>