Complex Analysis: Theory and Applications · Problem 5.5.2

Complex Integration — Howell & Matthews

Mathematics — Complex Analysis · inverse-trig-hyperbolic-identities

Problem

Establish the following identities. (a) arccos⁡z=−ilog⁡[z+i(1−z2)12]\arccos z = -i\log\left[z + i(1-z^2)^{\frac{1}{2}}\right]. (b) ddzarccos⁡z=−1(1−z2)12\dfrac{d}{dz}\arccos z = \dfrac{-1}{(1-z^2)^{\frac{1}{2}}}. (c) arctan⁡z=i2log⁡(i+zi−z)\arctan z = \dfrac{i}{2}\log\left(\dfrac{i+z}{i-z}\right). (d) ddzarctan⁡z=11+z2\dfrac{d}{dz}\arctan z = \dfrac{1}{1+z^2}. (e) arcsin⁡z+arccos⁡z=π2+2nπ\arcsin z + \arccos z = \dfrac{\pi}{2} + 2n\pi, where nn is an integer. (f) ddzarctanh⁡z=11−z2\dfrac{d}{dz}\operatorname{arctanh} z = \dfrac{1}{1-z^2}. (g) arcsinh⁡z=log⁡[z+(z2+1)12]\operatorname{arcsinh} z = \log\left[z + (z^2+1)^{\frac{1}{2}}\right]. (h) ddzarcsinh⁡z=1(z2+1)1/2\dfrac{d}{dz}\operatorname{arcsinh} z = \dfrac{1}{(z^2+1)^{1/2}}. (i) arccosh⁡z=log⁡[z+(z2−1)12]\operatorname{arccosh} z = \log\left[z + (z^2-1)^{\frac{1}{2}}\right]. (j) ddzarccosh⁡z=1(z2−1)12\dfrac{d}{dz}\operatorname{arccosh} z = \dfrac{1}{(z^2-1)^{\frac{1}{2}}}.

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