Trigonometry
Determine the exact values of cos(x+y)\cos\left(x+y\right)cos(x+y) and cos(x−y)\cos\left(x-y\right)cos(x−y).
cosx=−58\cos x=-\frac{\sqrt5}{8}cosx=−85, siny=−74\sin y=-\frac{\sqrt7}{4}siny=−47, xxx and yyy in quadrant III
cos(x+y)=359+3532\cos\left(x+y\right)=\frac{3\sqrt{59}+\sqrt{35}}{32}cos(x+y)=32359+35, cos(x−y)=359−3532\cos\left(x-y\right)=\frac{3\sqrt{59}-\sqrt{35}}{32}cos(x−y)=32359−35
cos(x+y)=359−3532\cos\left(x+y\right)=\frac{3\sqrt{59}-\sqrt{35}}{32}cos(x+y)=32359−35, cos(x−y)=359+3532\cos\left(x-y\right)=\frac{3\sqrt{59}+\sqrt{35}}{32}cos(x−y)=32359+35
cos(x+y)=−413+3532\cos\left(x+y\right)=\frac{-\sqrt{413}+3\sqrt5}{32}cos(x+y)=32−413+35, cos(x−y)=413+3532\cos\left(x-y\right)=\frac{\sqrt{413}+3\sqrt5}{32}cos(x−y)=32413+35
cos(x+y)=413+3532\cos\left(x+y\right)=\frac{\sqrt{413}+3\sqrt5}{32}cos(x+y)=32413+35, cos(x−y)=−413+3532\cos\left(x-y\right)=\frac{-\sqrt{413}+3\sqrt5}{32}cos(x−y)=32−413+35