SOLUTION: Please help me solve this equation;
I have to find the exact value of cos(13pi/12)
I have simplified it to cos (3pi/12+ 9pi/12) = cos(pi/4+3pi/4)
But then I get stuck and don
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Question 699222: Please help me solve this equation;
I have to find the exact value of cos(13pi/12)
I have simplified it to cos (3pi/12+ 9pi/12) = cos(pi/4+3pi/4)
But then I get stuck and don't know what to do from there.
Found 2 solutions by stanbon, Alan3354:
Answer by stanbon(75887) (Show Source): You can put this solution on YOUR website!
find the exact value of cos(13pi/12)
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The reference angle is (1/12)pi
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The original angle is in Quadrant #3 where the cos is negative.
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So, cos(13pi/12) = -cos((1/12)pi) = -0.9659
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Cheers,
Stan H.
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Answer by Alan3354(69443) (Show Source): You can put this solution on YOUR website!
Please help me solve this equation; **** Not an equation, no equal sign.
I have to find the exact value of cos(13pi/12)
I have simplified it to cos (3pi/12+ 9pi/12) = cos(pi/4+3pi/4)*****
--------------------------------------
= (4pi/12+ 9pi/12) = cos(pi/3+3pi/4)
---------------------
Use cos(A+B) = cos(A)cos(B) - sin(A)sin(B)
= cos(pi/3)*cos(3pi/4) - sin(pi/3)*sin(3pi/4)
= (1/2)*(-sqrt(2)/2) - sqrt(3)/2)*(sqrt(2)/2)
= -sqrt(2)/4 - sqrt(6)/4
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