Use the trigonometric identity:
sin^2(ax) = (1-cos(2ax))/2sin2(ax)=1−cos(2ax)2
So:
int sin^2(ax) dx= int (1-cos(2ax))/2dx∫sin2(ax)dx=∫1−cos(2ax)2dx
int sin^2(ax) dx= 1/2 int dx -1/2 int cos(2ax)dx∫sin2(ax)dx=12∫dx−12∫cos(2ax)dx
int sin^2(ax) dx= x/2 -1/(4a) int cos(2ax)d(2ax)∫sin2(ax)dx=x2−14a∫cos(2ax)d(2ax)
int sin^2(ax) dx= x/2 -1/(4a)sin(2ax) +C∫sin2(ax)dx=x2−14asin(2ax)+C
int sin^2(ax) dx= x/2 -1/(2a)sin(ax)cos(ax) +C∫sin2(ax)dx=x2−12asin(ax)cos(ax)+C
int sin^2(ax) dx= ( ax-sin(ax)cos(ax) )/(2a)+C∫sin2(ax)dx=ax−sin(ax)cos(ax)2a+C