Find the following in x + iy form

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  • Thread starter Logan Land
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In summary: Therefore, $\displaystyle \begin{align*} \sinh{ \left[ \ln{(2)} + \mathrm{i}\,\frac{\pi}{3} \right] } = \frac{3}{8} + \frac{5\sqrt{3}}{8} \, \mathrm{i} \end{align*}$In summary, we can find the value of sinh(ln2+ ipi/3) by using the identities for sinh and cosh, and then simplifying the expression to get the final answer of $\frac{3}{8}+ \frac{5\sqrt{3}}{8} \, \mathrm{i}$.
  • #1
Logan Land
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sinh(ln2+ ipi/3)

so I have a general formula of
sinh z= (e^z - e^-z)/2

so I obtained the following

sinh= (e^(ln2 + ipi/3) - e^-(ln2 + ipi/3))/2

sinh= (e^(ln2) e^(ipi/3) - e^(-ln2) e^(ipi/3))/2

e^(ln2)=2
e^(-ln2)=1/2
e^(ipi/3)= (1/2)+(isqrt3/2)
e^(-ipi/3)= (1/2)-(isqrt3/2)

so when I plug that in I seem to have the following

(2((1/2)+(i(sqrt3)/2)) - (1/2)((1/2)-(i(sqrt3)/2)))/2

which I think is

(1+(2i(sqrt3)/2) - (1/4)+((1/2)i(sqrt3)/2))/2

and from there if that is even correct I don't no where to go from there
I did wolfram and it said that the exact answer was

icos((pi/6)+iln2)

but I don't see how that is x +iy form
 
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  • #2
Using the identities $\displaystyle \begin{align*} \sinh{ \left( \alpha + \beta \right) } \equiv \sinh{\left( \alpha \right) } \cosh{ \left( \beta \right) } + \cosh{\left( \alpha \right) } \sinh{ \left( \beta \right) } \end{align*}$, $\displaystyle \begin{align*} \cosh{ \left( \mathrm{i}\,\alpha \right) } \equiv \cos{ \left( \alpha \right) } \end{align*}$ and $\displaystyle \begin{align*} \sinh{ \left( \mathrm{i}\,\alpha \right) } \equiv \mathrm{i}\,\sin{ \left( \alpha \right) } \end{align*}$ we have

$\displaystyle \begin{align*} \sinh{ \left[ \ln{(2)} + \mathrm{i}\,\frac{\pi}{3} \right] } &= \sinh{ \left[ \ln{(2)} \right] } \cosh{ \left( \mathrm{i}\,\frac{\pi}{3} \right) } + \cosh{ \left[ \ln{(2)} \right] } \sinh{ \left( \mathrm{i}\,\frac{\pi}{3} \right) } \\ &= \sinh{ \left[ \ln{(2)} \right] } \cos{ \left( \frac{\pi}{3} \right) } + \mathrm{i}\,\cosh{ \left[ \ln{(2)} \right] } \sin{ \left( \frac{\pi}{3} \right) } \\ &= \frac{1}{2}\sinh{ \left[ \ln{(2)} \right] } + \mathrm{i}\,\frac{\sqrt{3}}{2} \, \cosh{ \left[ \ln{(2)} \right] } \\ &= \frac{1}{2} \, \left[ \frac{\mathrm{e}^{\ln{(2)}} - \mathrm{e}^{-\ln{(2)}}}{2} \right] + \mathrm{i}\,\frac{\sqrt{3}}{2}\,\left[ \frac{e^{\ln{(2)}} + \mathrm{e}^{-\ln{(2)}}}{2} \right] \\ &= \frac{1}{2} \left[ \frac{2 - \mathrm{e}^{\ln{\left( 2^{-1} \right)}}}{2} \right] + \mathrm{i}\,\frac{\sqrt{3}}{2} \, \left[ \frac{2 + \mathrm{e}^{\ln{ \left( 2^{-1} \right) }}}{2} \right] \\ &= \frac{1}{2} \, \left( \frac{2 - \frac{1}{2}}{2} \right) + \mathrm{i}\,\frac{\sqrt{3}}{2} \, \left( \frac{2 + \frac{1}{2}}{2} \right) \\ &= \frac{3}{8} + \mathrm{i}\,\frac{5\,\sqrt{3}}{8} \end{align*}$
 
  • #3
Another way to proceed is as follows:

\(\displaystyle \exp(z)=\exp\left(\ln(2)+i\frac{\pi}{3}\right)=1+\sqrt{3}i\)

Hence:

\(\displaystyle \sinh(z)=\frac{1+\sqrt{3}i-\frac{1}{1+\sqrt{3}i}}{2}=\frac{-3+2\sqrt{3}i}{2\left(1+\sqrt{3}i\right)}\cdot\frac{1-\sqrt{3}i}{1-\sqrt{3}i}=\frac{3+5\sqrt{3}i}{8}=\frac{3}{8}+\frac{5\sqrt{3}}{8}i\)
 

Related to Find the following in x + iy form

1. How do I convert a complex number to the standard form "x + iy"?

To convert a complex number to the standard form "x + iy", simply separate the real and imaginary parts of the number. The real part will be represented by the variable x, and the imaginary part will be represented by iy. For example, if the complex number is 3 + 2i, the standard form would be 3 + 2i.

2. Can a complex number be in the form "iy + x"?

Yes, a complex number can be in the form "iy + x". This is known as the polar form of a complex number. In this form, the real part is represented by iy and the imaginary part is represented by x. It is also common to see this form written as x(cosθ + isinθ), where θ is the angle formed by the complex number on the complex plane.

3. How do I find the real and imaginary parts of a complex number in x + iy form?

To find the real and imaginary parts of a complex number in x + iy form, simply look at the coefficients in front of the variables. The coefficient in front of x represents the real part, and the coefficient in front of iy represents the imaginary part. For example, in the complex number 5 + 4i, the real part is 5 and the imaginary part is 4.

4. Is there a difference between "x + iy" and "iy + x" forms of a complex number?

No, there is no difference between "x + iy" and "iy + x" forms of a complex number. They both represent the same complex number, just in different forms. The choice of which form to use often depends on the context or the purpose of the problem.

5. Can a complex number have both a real and imaginary part of 0?

Yes, a complex number can have both a real and imaginary part of 0. In this case, the complex number would be 0 + 0i, which is also known as the origin on the complex plane. This means that the complex number has no real or imaginary part and is equivalent to the number 0 on the real number line.

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