Doug C. answered • 10/10/17
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Hi Imani,
Do you know the three identities for the cosine of twice an angle? If not, take time to locate them in your trig book.
One of them is cos2x = 1-2sin2x. Since you are given sinx = 9/41, substitute that value into the aforementioned identity and simplify.
Imani W.
10/10/17