Proving sin⁻¹(ix): 2nπ ± i log (√1+x²+x)

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In summary, to prove that $\sin^{-1}(ix)=2n\pi\pm i \log (\sqrt{1+x^2}+x)$, you can use the equation $\sin z = \frac{e^{i\ z}-e^{- i\ z}}{2\ i} = i\ x$ and solve for z by setting $e^{i\ z}=y$. This leads to the equation $y^{2} + 2\ x\ y -1 =0$, which can be solved for $y= - x \pm \sqrt{1+x^{2}}$. By substituting this into the equation for $\sin z$ and simplifying, you arrive at the equation $\sin
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Suvadip
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I need to prove
\(\displaystyle sin^{-1}(ix)=2n\pi\pm i log (\sqrt{1+x^2}+x)\)

I can prove \(\displaystyle sin^{-1}(ix)=2n\pi+ i log (\sqrt{1+x^2}+x)\)

How to prove the other part. Please help
 
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suvadip said:
I need to prove
\(\displaystyle sin^{-1}(ix)=2n\pi\pm i log (\sqrt{1+x^2}+x)\)

I can prove \(\displaystyle sin^{-1}(ix)=2n\pi+ i log (\sqrt{1+x^2}+x)\)

How to prove the other part. Please help

You have to find the z for which is...

$\displaystyle \sin z = \frac{e^{i\ z}-e^{- i\ z}}{2\ i} = i\ x$ (1)

Setting in (1) $\displaystyle e^{i\ z}=y$ You arrive to the equation...$\displaystyle y^{2} + 2\ x\ y -1 =0 $ (2)... which is solved for $\displaystyle y= - x \pm \sqrt{1+x^{2}}$ so that is... $\displaystyle \sin^{-1} (i\ x) = 2\ \pi\ i\ n - i\ \ln (- x \pm \sqrt{1+x^{2}}) = 2\ \pi\ i\ n + i\ \ln (x \pm \sqrt{1+x^{2}})$ (3)

Kind regards

$\chi$ $\sigma$
 

FAQ: Proving sin⁻¹(ix): 2nπ ± i log (√1+x²+x)

What is the meaning of sin⁻¹(ix)?

The notation sin⁻¹(ix) represents the inverse sine function, which is the angle whose sine is ix. In other words, it is the angle that, when plugged into the sine function, would give ix as the output.

How is sin⁻¹(ix) related to the complex logarithm?

The complex logarithm, denoted as log(z), is defined as the inverse function of the exponential function. In this case, the complex logarithm of (√1+x²+x) is equal to the inverse sine of ix, hence the notation sin⁻¹(ix).

Why is there a ± sign in the expression 2nπ ± i log (√1+x²+x)?

The ± sign represents the two possible solutions for the inverse sine function. Since the sine function is periodic with a period of 2π, there are infinitely many angles that have the same sine value. Therefore, the inverse sine function has two solutions for each input.

How can sin⁻¹(ix) be proved?

The proof of sin⁻¹(ix) involves using the definition of the inverse sine function and the properties of complex numbers, such as Euler's formula and the properties of logarithms. It is a complex and intricate proof that requires a strong understanding of complex analysis.

What is the significance of sin⁻¹(ix) in mathematics?

The inverse sine function, including its complex counterpart sin⁻¹(ix), is used in various fields of mathematics and physics. It has applications in trigonometry, calculus, differential equations, and signal processing, among others. It is also an important tool in solving complex equations and understanding the nature of complex numbers.

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