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=−4041\cos x=-\frac{40}{41}cosx=−4140, cosy=−725\cos y=-\frac{7}{25}cosy=−257, xxx and yyy in the third quadrant
cos(x+y)=10231025\cos\left(x+y\right)=\frac{1023}{1025}cos(x+y)=10251023, cos(x−y)=−8971025\cos\left(x-y\right)=-\frac{897}{1025}cos(x−y)=−1025897
cos(x+y)=−8971025\cos\left(x+y\right)=-\frac{897}{1025}cos(x+y)=−1025897, cos(x−y)=10231025\cos\left(x-y\right)=\frac{1023}{1025}cos(x−y)=10251023
cos(x+y)=4961025\cos\left(x+y\right)=\frac{496}{1025}cos(x+y)=1025496, cos(x−y)=641025\cos\left(x-y\right)=\frac{64}{1025}cos(x−y)=102564
cos(x+y)=641025\cos\left(x+y\right)=\frac{64}{1025}cos(x+y)=102564, cos(x−y)=4961025\cos\left(x-y\right)=\frac{496}{1025}cos(x−y)=1025496