Question 716870: Solve equation for Ɵ
cosƟ=-0.82
180°<Ɵ<270°
Answer by lwsshak3(11628)   (Show Source):
You can put this solution on YOUR website! Solve equation for Ɵ
cosƟ=-0.82
180°<Ɵ<270°
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Reference angle is in quadrant III where cos<0.
If you use the inverse cos key on the calculator and plug in -0.82, you get ≈145.08º which is not the correct answer because it is not in the specified quadrant.
To get the correct answer, plug in 0.82 to get 34.92º which is the reference angle in quadrant III, then add 180º to it to get 214.92º which is the correct answer for Ɵ.
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