The easiest angle to find is
v=3
in the first quadrant. When we draw the unit circle, we see that the angle which makes the same angle with the positive
x
-axis as
v=3, but is under the
x
-axis, also has a cosine value of
12
(same
x
-coordinate).
There are thus two angles,
v=3
and
v=2−3=53
which have their cosine value equal to
21.
3
