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December 6th, 2016, 11:49 PM  #1 
Member Joined: Nov 2014 From: SG Posts: 53 Thanks: 1  How to find A for this Question?
Given the following 50 = 144 cos^2(pi*A/41.35) How do I find A? 
December 7th, 2016, 12:33 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 16,585 Thanks: 1199 
What have you attempted?

December 7th, 2016, 12:49 AM  #3 
Member Joined: Nov 2014 From: SG Posts: 53 Thanks: 1 
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 
December 7th, 2016, 02:35 AM  #4 
Global Moderator Joined: Dec 2006 Posts: 16,585 Thanks: 1199 
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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