((SIN(α) + COS(α))^2 - SIN(2·α))/(CSC(α) + COT(α))^2 - (1 - COS(α))/(1 + COS(α))=
=((2·SIN(α)·COS(α) + 1) - SIN(2·α))/(1/SIN(α) + COT(α))^2 - (1 - COS(α))/(1 + COS(α))=
=1/(1/SIN(α) + COS(α)/SIN(α))^2 - (1 - COS(α))/(1 + COS(α))=
=1/((1 + COS(α))/SIN(α))^2 - (1 - COS(α))/(1 + COS(α))=
=SIN(α)^2/(1 + COS(α))^2 - (1 - COS(α))/(1 + COS(α))=
=(SIN(α)^2 - (1 - COS(α))·(1 + COS(α)))/(1 + COS(α))^2=
=(SIN(α)^2 - SIN(α)^2)/(1 + COS(α))^2=
=0