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https://puu.sh/y4Ose/987fce7804.png

 

Could anyone explain how I go about solving this? Thank you!

Guest Oct 23, 2017
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1+0 Answers

 #1
avatar+78577 
+2

cosθ = .7

 

cosθ +  cos ( θ  + 2pi) +  cos ( θ  + 4pi)

 

Use  cos (A + B)  =  [ cosAcosB  - sinAsinB ]

 

cos  θ    +  [ cosθ cos (2pi) - sinθ sin (2pi) ]   +  [ cosθ cos (4pi) - sinθ sin (4pi) ] 

 

cos  θ  +   [ cos θ     -  0 ]   +  [ cos θ     -  0 ]   

 

3 cosθ   

 

3 ( .7)    =     2.1

 

 

cool cool cool

CPhill  Oct 23, 2017

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