(b) $\int_{0}^{\frac{\pi}{2}}x\sin{x\ dx = \left\lbrack x( - \cos{x)} \right\rbrack_{0}^{\frac{\pi}{2}}} - \int_{0}^{\frac{\pi}{2}}{1( - \cos{x)dx}}$ $= 0 + \left\lbrack \sin x \right\rbrack_{0}^{\pi/2} = 1$
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Ph.D. in Physics with 19+ years of teaching experience.