Make a diagram of the unit circle with an angle θ in QI and its supplement 180° − θ in QII. Label the point on the terminal side of θ and the unit circle with (x, y) and the point on the terminal side of 180° − θ and the unit circle with (−x, y).

cos(180° − θ) = −cos θ

Question

Make a diagram of the unit circle with an angle θ in QI and its supplement 180° − θ in QII. Label the point on the terminal side of θ and the unit circle with (x, y) and the point on the terminal side of 180° − θ and the unit circle with (−x, y). 

cos(180° − θ) = −cos θ

noelgreco · Answer

Actually, you've got the 180-theta on the wrong side of the terinal side.|dw:1372633478543:dw|