Step-by-step explanation:
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144 - 56 = 88
88/144 simplified to -----> 11/18

On the unit cirlce, the cosine of an angle is negative whenever the angle falls in the interval

.
If you recall your special triangles, this cosine occurs for angles of

and

.
More generally, this occurs for

and

, where

is an integer.
Radius is the length of the line segment from the center of the circle to an endpoint on the circle and diameter is twice the length of the radius of the circle.