<PRE><B>Question 304682</B>
if tan0=8/3 in quadrant 3, what are cos20, sin0/2, cos0/2
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Angle is th (theta)
Hypotenuse = sqrt(73)
sin(th) = -8/sqrt(73) = -8sqrt(73)/73
cos(th) = -3/sqrt(73) = -3sqrt(73)/73
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cos(2th) = cos^2(th) - sin^2(th)
= 9/73 - 64/73 = -55/73
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cos(th/2) = sqrt((1+cos(th))/2)
= {{{ -sqrt((73 - 3sqrt(73))/146)}}}
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sin(th/2) = sqrt((1-cos(th))/2)
= {{{ -sqrt((73+3sqrt(73))/146)}}}



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