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December 6th, 2016, 10:49 PM   #1
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How to find A for this Question?

Given the following

50 = 144 cos^2(pi*A/41.35)

How do I find A?
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December 6th, 2016, 11:33 PM   #2
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What have you attempted?
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December 6th, 2016, 11:49 PM   #3
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Not sure if this is correct

This is my attempt so far.

sqrt(50/144) = cos (pi*A/41.35)
cos^-1 (sqrt(50/144) ) = pi*A/41.35

[ cos^-1 (sqrt(50/144) ) ] * 41.35 /pi = A
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December 7th, 2016, 01:35 AM   #4
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That gives A = 12.38106... (which is the smallest positive value for A).

More generally, A = ±12.38106... + 2k$\pi$, where k is an integer.
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