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The expression

cos x + cos 3x + cos 7x + cos 9x

can be written in the equivalent form a cos bx cos cx cos dx for some positive integers a, b, c, and d. 

Find a + b + c + d.

 Mar 31, 2020
edited by Guest  Mar 31, 2020
 #1
avatar+111321 
+1

See  here  :

 

https://web2.0calc.com/questions/halp_109#r3

 

 

cool cool cool

 Mar 31, 2020
 #2
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Thanks Heureka and CPhill!

 Mar 31, 2020
 #3
avatar+111321 
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HAHAHA!!!!.....most of the thanks  should go to Heureka!!!!

 

 

cool cool cool

CPhill  Mar 31, 2020

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