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November 14th, 2017, 04:21 AM  #1 
Newbie Joined: Nov 2017 From: Dresden, Saxony, Germany Posts: 2 Thanks: 0  Trigonometrical Equation, don't know how to simplify it
Hi everyone. I have an expression cos(f)*(sin(g)*cos(m)*cos(l) + sin(g)*sin(m)*sin(l)) + cos(g)*sin(f) which is equal to cos(g)*sin(f)  cos(f)*sin(g)*cos(l  m) according to Wolfram Alpha's CAS. I have no clue how to get there. Thanks in advance, Peter Last edited by skipjack; November 14th, 2017 at 05:09 AM. 
November 14th, 2017, 05:08 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 19,994 Thanks: 1856 
cos(f)*(sin(g)*cos(m)*cos(l) + sin(g)*sin(m)*sin(l)) = sin(g)cos(f)(cos(m)cos(l) + sin(m)sin(l)) = sin(g)cos(f)cos(l  m) Now add cos(g)sin(f) to both sides. 
November 16th, 2017, 03:08 AM  #3 
Newbie Joined: Nov 2017 From: Dresden, Saxony, Germany Posts: 2 Thanks: 0 
Thank you so much skipjack 

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equation, simplify, trigonometrical 
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