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Ace.
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Homework Statement
If cosθ = -5/13 and 0 <= θ <= 2π, what are possible values of θ?
Homework Equations
The Attempt at a Solution
θ is in quadrant 2 or 3
in quadrant 2:
related acute = cos[itex]^{-1}[/itex](5/13)
= 1.18
θ = π - 1.18
= 1.96 radians
in quadrant 3:
related acute angle = 1.18
θ = π + 1.18
= 4.32 radians
Those are the two values I got for θ. But my book says the answer is 5.14. Can you tell me where I am going wrong?