Which of the following is a solution to sin x = 2 in the complex numbers?
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Why we can't take z = r.cisx = 2i±√3i , which is more general form of a complex number
Here's a really lazy method. In the example we already get the solution for cos x = 2 , which is x = 2 k π ± ln 2 ± 3 and x = 2 k π ∓ ln 2 ± 3 . Fortunately, of the options provided, the part outside the logarithm has magnitude less than 2 π , so we can drop all the 2 k π to get x = ± ln 2 ± 3 or x = ∓ ln 2 ± 3 . Now, I used the complimentary angle identity: sin x = cos 2 π − x , letting sin x = 2 : 2 π − x = ± ∓ ln 2 ± 3 , so we have x = 2 π ± ∓ ln 2 ± 3 . Check the options and only one match this form.
Are the options 2 π ± i ( ln ( 2 + 3 ) ) and 2 π ± i ( ln ( 2 − 3 ) ) identical?
Yes they are same.
Why have we not considered the cases in which there is 3 π / 2 instead of π / 2 . If we do then we get four solutions to the given question. Do you have any idea about this?
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I don't think that replacing π / 2 by 3 π / 2 are still solutions. Can you elaborate more on it?
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Check the link which I have provided in my answer to get an idea of what I am saying.
The answer gets very complicated difficult for me to type in. A direct link to a website is given which provides the direct formula and its proof for these sin problems.
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