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Select one or more expressions that together represent all solutions to the equation. Your answer should be in degrees.
Assume n is any integer.

7cos(5x)+9=12

Choose all answers that apply:

Choose all answers that apply:

A −115.38​∘​​+n⋅360​∘​​

B −16.48​∘​​+n⋅180​∘​​

C −12.92​∘​​+n⋅72​∘​​

D 12.92​∘​​+n⋅72​∘​​

E 16.48​∘​​+n⋅180​∘

F 115.38​∘​​+n⋅360​∘

Guest Nov 21, 2017
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1+0 Answers

 #1
avatar+79846 
+1

7cos(5x) + 9 =12      subtract 9 from both sides

 

7cos(5x)  =  3          divide both sides by 7

 

cos(5x)  =  3/7

 

Let q  = 5x

 

So ....cos ( q )  =   3/7    at  q   ≈  64.623° + n360°  and at  q  =   -64.623° + n360°

 

So   

 

q  =  5x =  64.623° + n360°

Divide by 5

x = 12.92° + n72°

 

And 

q =  5x =  64.623° + n360°

Divide by 5

x = -12.92° + n72°

 

 

cool cool cool

CPhill  Nov 21, 2017

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