the question is: find the exact value of sin(x-y) when sinx=8/17 and cos=5/13 need help
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Use the formula $\displaystyle \sin(x-y)=\sin x\cos y-\sin y\cos x$.
Originally Posted by red_dog Use the formula $\displaystyle \sin(x-y)=\sin x\cos y-\sin y\cos x$. but you only have sinx and cosy you dont have siny and cosx
$\displaystyle \cos x=\pm\sqrt{1-\sin^2x}, \ \sin y=\pm\sqrt{1-\cos^2y}$ To choose the sign before the radical, you have to know in which quadrant are x and y.
i wasnt taught the radical yet, is there another way like guess and check?
Originally Posted by pogiphilip i wasnt taught the radical yet, is there another way like guess and check? Hi Do you know the domain for x and y ? ie 0<x<90 ??
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