Is the Complex Conjugate of Sin Equal to Sin of the Conjugate?

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SUMMARY

The discussion centers on the equality of the complex conjugate of the sine function, specifically whether (\sin{z})^* equals \sin{z^*}. The conclusion is that they are not equivalent due to the incorrect application of the sine function's definition. The correct definition is \sin{z} = \frac{1}{2i} (e^{iz} - e^{-iz}), which incorporates the imaginary unit "i" in the denominator, resolving the sign discrepancy. This distinction is crucial for accurately evaluating complex functions.

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Homework Statement



does (\sin{z})^* = \sin{z^*}?

(where z is a complex number)

Homework Equations



\sin{z} = \frac{1}{2} (e^{iz} - e^{-iz})

The Attempt at a Solution



(\sin{z})^* = \frac{1}{2} (e^{iz} - e^{-iz})^*<br /> = \frac{1}{2} (e^{-iz^*} - e^{iz^*}) <br /> = -\frac{1}{2} (e^{iz^*} - e^{-iz^*})<br /> = -sin(z^*)

...but my teacher told us ahead of time that they should be equivalent. I'm not seeing my mistake. Thank you for your time and energy.

I will also note that the same problem for cos only worked out to be equivalent because of the commutative rule. This doesn't work for sin, since it's exponential terms differ in their signs.
 
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Here's your error:
\sin{z} = \frac{1}{2} (e^{iz} - e^{-iz})
is wrong.

\sin{z} = \frac{1}{2i} (e^{iz} - e^{-iz})


It's the "i" in the denominator that will take care of that sign.
 
ah, right, old habit from the days of real.

Thank you HallsofIvy
 

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