2cos2(x)-1=cos(2x)=cos2(x)-sin2(x)=(cos(x)+sin(x))(cos(x)-sin(x)).
4tan(π/4-x)=4(1-tan(x))/(1+tan(x))=4(cos(x)-sin(x))/(cos(x)+sin(x));
sin2(π/4+x)=½(cos(x)+sin(x))2=½(1+sin(2x)).
4tan(π/4-x)·sin2(π/4+x)=2(cos(x)-sin(x))(1+sin(2x))/(cos(x)+sin(x)).
(2cos2(x)-1):[4tan(π/4-x)·sin2(π/4+x)]=(2cos2(x)-1)/[4tan(π/4-x)·sin2(π/4+x)],
(cos(x)+sin(x))(cos(x)-sin(x))/2(cos(x)-sin(x))(1+sin(2x))/(cos(x)+sin(x))=
(cos(x)+sin(x))2/2(1+sin(2x))=(1+sin(2x))/2(1+sin(2x))=1/2 or 1:2.