Hyperbolic functions

The hyperbolic functions sinhx\sinh x, coshx\cosh x, and tanhx\tanh x are defined using the exponential function exe^x:
  • sinhx=exex2\displaystyle \sinh x=\frac{e^x-e^{-x}}{2}
  • coshx=ex+ex2\displaystyle \cosh x=\frac{e^x+e^{-x}}{2}
  • tanh=sinhxcoshx=exexex+ex\displaystyle \tanh=\frac{\sinh x}{\cosh x}=\frac{e^x-e^{-x}}{e^x+e^{-x}}
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Practice: Hyperbolic Function
Prove the following.
a) cosh2xsinh2x=1\cosh^2x-\sinh^2x=1
b) ddx(sinhx)=coshx\displaystyle \frac{d}{dx}\left(\sinh x\right)=\cosh x
c) ddx(coshx)=sinhx\displaystyle \frac{d}{dx}\left(\cosh x\right)=\sinh x
d) ddx(tanhx)=1cosh2x\displaystyle \frac{d}{dx}\left(\tanh x\right)=\frac{1}{\cosh^2x}