Question

Вычислить интеграл функции, №1

Answer 1

$a\neq 0:\;\;\;\;x=a*tgt=>t=arctg \dfrac{x}{a}=>dx=a*\dfrac{1}{cos^2t}dt\\ \int\dfrac{dx}{(x^2+a^2)^\frac{3}{2}}=\int \dfrac{adt}{cos^2t*a^3*(1+tg^2t)^\frac{3}{2}}=\int \dfrac{costdt}{a^2}=\dfrac{1}{a^2}sint+C=\dfrac{1}{a^2}\dfrac{\frac{x}{a}}{\sqrt{(\frac{x}{a})^2+1}}+C=\dfrac{x}{a^2\sqrt{x^2+a^2}}+C\\ a=0:\;\;\;\;\int\dfrac{dx}{(x^2)^\frac{3}{2}}=\int \dfrac{dx}{|x|^3}=\int \dfrac{|x|}{x}*\dfrac{x}{|x|}*\dfrac{1}{x^2|x|}dx=\dfrac{x}{|x|}*\int \dfrac{1}{x^3}dx=-\dfrac{1}{2x^2}\dfrac{x}{|x|}+C=$$=-\dfrac{1}{2x|x|}+C$