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定積分・広義積分計算機
定積分と広義積分を手順を追って計算する
この計算機は、定積分（すなわち上下限のある積分）を、広義積分も含めて、解法手順を示しながら計算を試みます。
Solution
Your input: calculate $$$\int_{\infty}^{0}\left( x e^{- x^{2}} \right)dx$$$
First, calculate the corresponding indefinite integral: $$$\int{x e^{- x^{2}} d x}=- \frac{e^{- x^{2}}}{2}$$$ (for steps, see indefinite integral calculator)
Since the upper bound is less than the lower, according to the property of integrals, we can swap them and change the sign:
$$$\int_{\infty}^{0}\left( x e^{- x^{2}} \right)dx=-\int_{0}^{\infty}\left( x e^{- x^{2}} \right)dx$$$
Since there is infinity in the upper bound, this is improper integral of type 1.
To evaluate an integral over an interval, we use the Fundamental Theorem of Calculus. However, we need to use limit if an endpoint of the interval is special (infinite).
$$$\int_{0}^{\infty}\left( x e^{- x^{2}} \right)dx=\lim_{x \to \infty}\left(- \frac{e^{- x^{2}}}{2}\right)-\left(- \frac{e^{- x^{2}}}{2}\right)|_{\left(x=0\right)}=\frac{1}{2}$$$
Do not forget about the minus sign: $$$\int_{\infty}^{0}\left( x e^{- x^{2}} \right)dx=-\int_{0}^{\infty}\left( x e^{- x^{2}} \right)dx=- \frac{1}{2}$$$
Answer: $$$\int_{\infty}^{0}\left( x e^{- x^{2}} \right)dx=- \frac{1}{2}=-0.5$$$