1）D=(sin x-sin y)(sin x+sin y)-(cos x-cos y)(cos x+cos y)
=sin² x-sin² y-cos ²x+cos²y
=(cos² y-sin² y)-(cos² x-sin²x)
=cos 2y-cos 2x
2) D=e^(x+y)*e^(x-y)-[(e^x)+1][(e^x)-1]
=e^(x+y+x-y)-e^2x+1
=e^2x-e^2x+1
=1
1）D=(sin x-sin y)(sin x+sin y)-(cos x-cos y)(cos x+cos y)
=sin² x-sin² y-cos ²x+cos²y
=(cos² y-sin² y)-(cos² x-sin²x)
=cos 2y-cos 2x
2) D=e^(x+y)*e^(x-y)-[(e^x)+1][(e^x)-1]
=e^(x+y+x-y)-e^2x+1
=e^2x-e^2x+1
=1