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In mathematics, the inverse of a function is a function that, in some fashion, "undoes" the effect of (see inverse function for a formal and detailed definition). The inverse of is denoted . The statements and are equivalent. Their two derivatives, assuming they exist, are reciprocal, as the Leibniz notation suggests; that is: : This is a direct consequence of the chain rule, since : and the derivative of with respect to is 1. Writing explicitly the dependence of on and the point at which the differentiation takes place and using Lagrange's notation, the formula for the derivative of the inverse becomes : Geometrically, a function and inverse function have graphs that are reflections, in the line . This reflection operation turns the gradient of any line into its reciprocal. Assuming that has an inverse in a neighbourhood of and that its derivative at that point is non-zero, its inverse is guaranteed to be differentiable at and have a derivative given by the above formula. ==Examples== * (for positive ) has inverse . : : At , however, there is a problem: the graph of the square root function becomes vertical, corresponding to a horizontal tangent for the square function. * (for real ) has inverse (for positive ) : : 抄文引用元・出典: フリー百科事典『 ウィキペディア(Wikipedia)』 ■ウィキペディアで「Inverse functions and differentiation」の詳細全文を読む スポンサード リンク
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