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# differentiating - product rule I think?? watch

1. Hi,

can someone helkp pls.

differentiate with respect to x:

x^2sinx;

I got as far as vdu + udv, stickin the stuff, sin comes out as cos , but I get stuck

Is this the right approach.

2. yes.

u=x^2, v= sinx

d(uv)/dx = u(dv/dx) + v(du/dx) = x^2cosx + 2xsinx

= x(xcosx + 2sinx)
3. (Original post by rts)
yes.

u=x^2, v= sinx

d(uv)/dx = u(dv/dx) + v(du/dx) = x^2cosx + 2xsinx

= x(xcosx + 2sinx)
cool, the answer in the book is 1 - 3x^2

4. Aren't your exams over yet?
5. (Original post by austinmetro)
cool, the answer in the book is 1 - 3x^2

The books wrong then, the answer is:

x(2sinx + xcosx)
6. y = (x^2)sin x

u = x^2
v = sin x

y = uv

du/dx = 2x
dv/dx = cos x

dy/dx = u(dv/dx) + v(du/dx)
dy/dx = (x^2)(cos x) + (sin x)(2x)
dy/dx = (x^2)cos x + (2x)sin x
dy/dx = x(x cos x + 2 sin x)

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