Trigonometry
Find the exact value of cos(x−y)\cos\left(x-y\right)cos(x−y) . Use a trigonometric identity.
cosx=511\cos x=\frac{5}{11}cosx=115, siny=−18\sin y=-\frac18siny=−81, xxx in fourth quadrant, yyy in third quadrant
−15771-\frac{15\sqrt7}{71}−71157
−157+4688\frac{-15\sqrt7+4\sqrt6}{88}88−157+46
15771\frac{15\sqrt7}{71}71157
157−4688\frac{15\sqrt7-4\sqrt6}{88}88157−46