Соs(x+1)cos(x-1)=
sin(m+n)sin(m-n)=
sin(1-x)×cos(1-2x)=

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Объяснение:

1)cos(x+1)cos(x-1)=1/2(cos(x+1-x+1)+c0s(x+1+x-1))=1/2(cos2+cos2x)

2)sin(m+n)sin(m-n)=1/2(cos(m+n-m+n)-cos(m+n+m-n))=1/2(cos2n-cos2m);

3)sin(1-x)·cos(1-2x)=1/2(sin(1-x-1+2x)+sin(1-x+1-2x))=1/2(sinx+sin(2-3x)).