can someone help me here? i know these are simple but i can't get it. Find sin(x/2) when cos(x)=3/7. and find cos(x/2) when sin(x)=5/12
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Originally Posted by jarny can someone help me here? i know these are simple but i can't get it. Find sin(x/2) when cos(x)=3/7. and find cos(x/2) when sin(x)=5/12 use the half-angle formulas: $\displaystyle \sin \frac x2 = \pm \sqrt{\frac {1 - \cos x}2}$ and $\displaystyle \cos \frac x2 = \pm \sqrt{\frac {1 + \cos x}2}$ also, $\displaystyle \sin^2 x + \cos^2 x = 1$ will come in handy for the second one
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