Question 1033133
 I don't really understand the double-angle or the half-angle formula. Here are some problems I need to do: 
1. If cos t = sqrt(2)/2
and t is a fourth-quadrant angle, evaluate sin 2x.
cos = x/r, so x = sqrt(2), r = 2
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Because t is in QIV  y = -sqrt[2+4] = -sqrt(6)
So sin(t) = y/r = -sqrt(6)/2
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Ans: sin(2t) = 2*sin(t)*cos(t) = 2[-sqrt(6)/2 *sqrt(2)/2] = -sqrt(12)/2
= -2sqrt(3)/2 = -sqrt(3)
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2. If t is a first-quadrant angle in standard position with P(u, v) = (3, 4), evaluate tan t
Tan(t) = y/x = 4/3
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Cheers,
Stan H.