Question

Find the measures of all possible angles, rounded to the nearest degree, where cos x = 0.789 and 0° ≤ x ≤ 360°?

Answer 1

\[x=\cos^{-1} (0,789)\]
x=38

Answer 2

and x=322

Answer 3

There would be two of these angles. One would be in Quadrant I and the other in Quadrant IV because the cosine is positive in these two quadrants. So enter .789 into your calculator, push the inverse cosine button and you will get 38 degrees. But don't forget the one in the fourth quadrant which can be found by subtracting 38 from 360.

Answer 4

because cos(2pi-theta)=cos(theta)