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).
sinx=313\sin x=\frac{3}{13}sinx=133, siny=−27\sin y=-\frac27siny=−72, xxx in quadrant I and yyy in quadrant III
cos(x+y)=6−60291\cos\left(x+y\right)=\frac{6-60\sqrt2}{91}cos(x+y)=916−602, cos(x−y)=−6−60291\cos\left(x-y\right)=\frac{-6-60\sqrt2}{91}cos(x−y)=91−6−602
cos(x+y)=−6−60291\cos\left(x+y\right)=\frac{-6-60\sqrt2}{91}cos(x+y)=91−6−602, cos(x−y)=6−60291\cos\left(x-y\right)=\frac{6-60\sqrt2}{91}cos(x−y)=916−602
cos(x+y)=−810−9591\cos\left(x+y\right)=\frac{-8\sqrt{10}-9\sqrt5}{91}cos(x+y)=91−810−95, cos(x−y)=810−9591\cos\left(x-y\right)=\frac{8\sqrt{10}-9\sqrt5}{91}cos(x−y)=91810−95
cos(x+y)=810−9591\cos\left(x+y\right)=\frac{8\sqrt{10}-9\sqrt5}{91}cos(x+y)=91810−95, cos(x−y)=−810−9591\cos\left(x-y\right)=\frac{-8\sqrt{10}-9\sqrt5}{91}cos(x−y)=91−810−95