Question Number 11403 by JAZAR last updated on 24/Mar/17

how can demonstred that   cos(2x)−sin(2x)−1=−cos^2 x

Commented bysm3l2996 last updated on 24/Mar/17

I think that equation is not correct  because cos(2π)−sin(2π)−1=0≠−cos^2 (π)