Trigonometry
Find the exact value of cos(x−y)\cos\left(x-y\right)cos(x−y) . Use a trigonometric identity.
siny=−37\sin y=-\frac37siny=−73, cosx=−29\cos x=-\frac29cosx=−92, xxx in second quadrant, yyy in third quadrant
−377+41063\frac{-3\sqrt{77}+4\sqrt{10}}{63}63−377+410
−45763-\frac{4\sqrt{57}}{63}−63457
377−41063\frac{3\sqrt{77}-4\sqrt{10}}{63}63377−410
45763\frac{4\sqrt{57}}{63}63457