sin^2(x+y)-cos(x+y)sin(x+y)-3cos^2(x+y)的值急用

sin^2(x+y)-cos(x+y)sin(x+y)-3cos^2(x+y)的值急用
sin^2(x+y)-cos(x+y)sin(x+y)-3cos^2(x+y)的值
急用

sin^2(x+y)-cos(x+y)sin(x+y)-3cos^2(x+y)的值急用
原式=sin²(x+y)+cos²(x+y)-1/2*sin[2(x+y)]-4cos²(x+y)
=1-1/2*sin(2x+2y)-4[1+cos(2x+2y)]/2
=-1/2*sin(2x+2y)-2cos(2x+2y)-1

=2007+1-2009分之2008
=2007+2009分之1
=2007又2009分之1
原式=(x²-2xy+y²+x²-y²)÷2x
=(2x²-2xy)÷2x
=2x²÷2x-2xy÷2x
=x-y
=3-(-2)
=3+2
=5