JAMB 2013 · UTME · Q36

If y=xsin⁡xy = x\sin x, find dydx\dfrac{dy}{dx}.

Worked solution (try it first)
  1. Product rule with u=xu = x and v=sin⁡xv = \sin x: u′=1u' = 1 and v′=cos⁡xv' = \cos x.
  2. dydx=u′v+uv′\frac{dy}{dx} = u'v + uv'
    =sin⁡x+xcos⁡x= \sin x + x\cos x, option B.

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