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39 votes
Find the value of 2cosx+1=0;0 less than x less than 360°

User JeremiahDotNet
by
3.1k points

1 Answer

11 votes
11 votes

Answer:

120°; 240°

Explanation:

Let's first solve for
cosx:
2cosx=-1 \rightarrow cosx=-\frac12 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
-\frac12 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°.

Find the value of 2cosx+1=0;0 less than x less than 360°-example-1
User Tnishada
by
2.7k points