Derivative Trig Functions - Math2.org
Proof of cos(x): from the derivative of sine This can be derived just like sin(x) was derived or more easily from the result of sin(x) Given: sin(x) = cos(x); Chain Rule. Solve: cos(x) = sin(x + PI/2) cos(x) = sin(x + PI/2) = sin(u) * (x + PI/2) (Set u = ...