Use the symmetry of the graphs of the sine and cosine functions as an aid in evaluating each definite integral.

(a) Integral of sinx*dx from -pi/4 to pi/4

(b) Integral of cosx*dx from -pi/4 to pi/4

(c) Integral of cosx*dx from -pi/2 to pi/2

(d) Integral of sinx*cosx*dx from -pi/2 to pi/2