Respuesta :
[tex]y=\ln\dfrac{x-\sqrt{x^2-4}}2[/tex]
[tex]\implies e^y=\dfrac{x-\sqrt{x^2-4}}2[/tex]
[tex]\implies e^{-y}=\dfrac2{x-\sqrt{x^2-4}}[/tex]
[tex]\implies e^y+e^{-y}=\dfrac{x-\sqrt{x^2-4}}2+\dfrac2{x-\sqrt{x^2-4}}[/tex]
[tex]e^y+e^{-y}=\dfrac{(x-\sqrt{x^2-4})^2+4}{2(x-\sqrt{x^2-4})}[/tex]
[tex]e^y+e^{-y}=\dfrac{2x(x-\sqrt{x^2-4})}{2(x-\sqrt{x^2-4})}[/tex]
[tex]e^y+e^{-y}=x[/tex]
[tex]\implies y=e^x+e^{-x}=2\cosh x[/tex] is the inverse, though this isn't exactly right because [tex]2\cosh x[/tex] is not invertible over its entire domain. So we need to restrict it appropriately. We have [tex]\ln\dfrac{x-\sqrt{x^2-4}}2\le0[/tex] for all [tex]x\ge2[/tex], which means we desire [tex]2\cosh x\ge2[/tex] for all [tex]x\le0[/tex], and so the restricted domain needs to be all non-positive real numbers.
[tex]\implies e^y=\dfrac{x-\sqrt{x^2-4}}2[/tex]
[tex]\implies e^{-y}=\dfrac2{x-\sqrt{x^2-4}}[/tex]
[tex]\implies e^y+e^{-y}=\dfrac{x-\sqrt{x^2-4}}2+\dfrac2{x-\sqrt{x^2-4}}[/tex]
[tex]e^y+e^{-y}=\dfrac{(x-\sqrt{x^2-4})^2+4}{2(x-\sqrt{x^2-4})}[/tex]
[tex]e^y+e^{-y}=\dfrac{2x(x-\sqrt{x^2-4})}{2(x-\sqrt{x^2-4})}[/tex]
[tex]e^y+e^{-y}=x[/tex]
[tex]\implies y=e^x+e^{-x}=2\cosh x[/tex] is the inverse, though this isn't exactly right because [tex]2\cosh x[/tex] is not invertible over its entire domain. So we need to restrict it appropriately. We have [tex]\ln\dfrac{x-\sqrt{x^2-4}}2\le0[/tex] for all [tex]x\ge2[/tex], which means we desire [tex]2\cosh x\ge2[/tex] for all [tex]x\le0[/tex], and so the restricted domain needs to be all non-positive real numbers.