When w = 0, the indefinite integral is y = C；; (c is an arbitrary constant);

When w≠0, y = (-A/w)*cos(wx)+C (arbitrary constant)

Process:

When w = 0, y = 0 and the derivative of any constant is 0; So y = C；; ;

W≠0, because the derivative of cos(wx) is -wsin(wx), so the derivative of (-A/w)*cos(wx) is asin (wx);

Adding an arbitrary constant c after it is the indefinite integral of this expression: y = (-a/w) * cos (wx)+c.