(Sin^2 + 2sincos + cos^2) - 1 = sin^2 + 2sincos + cos^2 - 1= sin^2 + cos^2 + 2sincos - 1= 1 + 2sincos - 1= 2sin*cos
(Sin^2 + 2sincos + cos^2) - 1 = sin^2 + 2sincos + cos^2 - 1
= sin^2 + cos^2 + 2sincos - 1
= 1 + 2sincos - 1
= 2sin*cos