Do you have integration by parts?
If so: ∫u dv = u·v -∫v du
Let u = x --> du = dx
Let dv = sin(7x)dx --> v = -(1/7)cos(7x)
Substituting: ∫xsin(7x)dx = -(x/7)cos(7x) - ∫-(1/7)cos(7x)dx
∫xsin(7x)dx = -(x/7)cos(7x) +(1/7) ∫cos(7x)dx
∫xsin(7x)dx = -(x/7)cos(7x) + (1/49)sin(7x) + C
Do you have integration by parts?
If so: ∫u dv = u·v -∫v du
Let u = x --> du = dx
Let dv = sin(7x)dx --> v = -(1/7)cos(7x)
Substituting: ∫xsin(7x)dx = -(x/7)cos(7x) - ∫-(1/7)cos(7x)dx
∫xsin(7x)dx = -(x/7)cos(7x) +(1/7) ∫cos(7x)dx
∫xsin(7x)dx = -(x/7)cos(7x) + (1/49)sin(7x) + C