[sin^2(x)+cos^2(x)+cos^2(x)-sin^2(x)-2sin(x)*cos(x)]/[cos(x)+sin(x)]=[-2cos(x)*(cos(x)+sin(x))]/[cos(x)+sin(x)]=-2cos(x)
[sin^2(x)+cos^2(x)+cos^2(x)-sin^2(x)-2sin(x)*cos(x)]/[cos(x)+sin(x)]=[-2cos(x)*(cos(x)+sin(x))]/[cos(x)+sin(x)]=-2cos(x)