Answer
$\dfrac{1}{8}(8-4\pi+\pi^2)$
Work Step by Step
$\int_{0}^{\frac{\pi}{2}}\int_{0}^{x}x\sin y\,dy\,dx=-\int_{0}^{\frac{\pi}{2}}x\biggl[\cos y\biggr]_{0}^{x}\, dx=-\int_{0}^{\frac{\pi}{2}}x\cos x-x\, dx=\dfrac{1}{8}(8-4\pi+\pi^2)$
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