May 1st, 2017, 06:13 AM  #1 
Member Joined: Sep 2016 From: zambia Posts: 31 Thanks: 0  trigonometry 
May 1st, 2017, 10:03 AM  #2 
Math Team Joined: Jul 2011 From: Texas Posts: 2,678 Thanks: 1339 
What is the symbol circled in yellow? It would help if you typed out the equations ... Last edited by skeeter; May 1st, 2017 at 10:17 AM. 
May 1st, 2017, 10:36 AM  #3 
Math Team Joined: Oct 2011 From: Ottawa Ontario, Canada Posts: 11,087 Thanks: 723 
WHY have we yet not told this student to post CLEARLY plus show his work? All his posts so far show no work... May I? Jeho, please show CLEAR attachments PLUS your work. Thank you in advance. NOTE: your handwriting is worse than mine! 
May 6th, 2017, 11:01 PM  #4 
Newbie Joined: Jun 2016 From: Hong Kong Posts: 20 Thanks: 2 
$\cos(\frac{\pi}{4}\theta)=\frac{AB}{AE}$ $\cos(\frac{\pi}{4}\theta)=\frac{1}{2}(1+\sin 2\theta)$ 
May 7th, 2017, 09:39 AM  #5 
Global Moderator Joined: Dec 2006 Posts: 18,250 Thanks: 1439 
AE = AB/(AB/AE) = a/cos($\pi$/4  Ï•) AEÂ² = 2aÂ²/(2cosÂ²(pi/4  Ï•)) $\ \ \ \ \ \ \ \ $= 2aÂ²/(cos($\pi$/2  2Ï•) + 1) (because cos2Î¸ â‰¡ 2cosÂ²Î¸  1) $\ \ \ \ \ \ \ \ $= 2aÂ²/(1 + sin(2Ï•)) 

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