Answer:
120°; 240°
Step-by-step explanation:
Let's first solve for [tex]cosx[/tex]: [tex]2cosx=-1 \rightarrow cosx=-\frac12[/tex] At this point it's just a matter of drawing a circle, and mark where the angle is(please excuse my paint skills, but free hand drawing would be even worse). Red line, is [tex]-\frac12[/tex] on the cosines, and both the green and blue lines are valid solutions. The green line is a quarter of a circle, plus 30°, or 120°. The blue one is 3/4 of a circle, minus 30 degrees, or 240°.
