using cosh and inverse cosh in matlab
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mohammed hussein
on 11 Feb 2022
Commented: Steven Lord
on 11 Feb 2022
Hi all
i have problem using cosh and cosh^-1 in matlab . in my program i have to solve complex number using cosh and i have to reused cosh^-1 to get the same number but i couldnt . for example
A=5+5i
B= cosh(A) it gives (21.0506 -71.1553i)
A=acosh(B) it gives (5.0000 - 1.2832i) which is not the same A (5+5i)
how can i solve this problem
thank you
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Accepted Answer
Steven Lord
on 11 Feb 2022
What problem?
A1 = 5+5i
A2 = acosh(cosh(A1))
(A2-A1)/(2i*pi)
Remember that as stated on Wikipedia "hyperbolic functions are periodic with respect to the imaginary component, with period " So you received a correct answer (if you added one period, , to A2 you get A1 or close enough) even if it wasn't the correct answer you expected.
A1 - (A2 + 2i*pi)
2 Comments
Steven Lord
on 11 Feb 2022
Without more information, you can't.
As a simpler example, I'm thinking of a number that gives the result 4 when squared. What is my number?
You may say that the answer is 2. That is one correct answer. A different correct answer is -2.
It is impossible for you to tell whether the number I was thinking of was 2 or -2.
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