Danh Sách Tích Phân – Wikipedia Tiếng Việt

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d d x ( 1 a arctg x a + C ) = d d x ( 1 a arctg x a ) = 1 a ⋅ d d ( x a ) ( arctg ⁡ x a ) ⋅ d d x ( x a ) = 1 a ⋅ 1 1 + x 2 a 2 ⋅ 1 a = 1 a 2 ⋅ a 2 + x 2 a 2 = 1 a 2 + x 2 {\displaystyle {d \over dx}\,\left({1 \over a}\,\operatorname {arctg} \,{\frac {x}{a}}+C\right)={d \over dx}\,\left({1 \over a}\,\operatorname {arctg} \,{\frac {x}{a}}\right)={\frac {1}{a}}\cdot {d \over d\left({x \over a}\right)}\left(\operatorname {arctg} {\frac {x}{a}}\right)\cdot {d \over dx}\left({x \over a}\right)={\frac {1}{a}}\cdot {\frac {1}{1+{\frac {x^{2}}{a^{2}}}}}\cdot {\frac {1}{a}}={\frac {1}{a^{2}\cdot {\frac {a^{2}+x^{2}}{a^{2}}}}}={\frac {1}{a^{2}+x^{2}}}}

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