∫01x1−x2 dx=\displaystyle \int_0^1 x \sqrt{1-x^2}\, dx =∫01x1−x2dx=A111B12\frac{1}{2}21C13\frac{1}{3}31check_circleD23\frac{2}{3}32ExplanationLet u=1−x2u=1-x^2u=1−x2, du=−2x dxdu=-2x\,dxdu=−2xdx. Limits: x=0→u=1x=0\to u=1x=0→u=1, x=1→u=0x=1\to u=0x=1→u=0. Then ∫10u⋅(−du/2)=12∫01u1/2 du=13\int_1^0 \sqrt{u}\cdot(-du/2) = \frac{1}{2}\int_0^1 u^{1/2}\,du = \frac{1}{3}∫10u⋅(−du/2)=21∫01u1/2du=31.