Answer:
(c) -0.9682
Explanation:
In quadrant II, the cosine is negative. Solving the given equation for the cosine gives ...
sin²(A) +cos²(A) = 1
cos²(A) = 1 -sin²(A)
cos(A) = -√(1 -sin²(A)) = -√(1 -(1/4)²) = -√(15/16) ≈ -0.9682
_____
The coordinates of a point on the unit circle are (cos(α), sin(α)). The attachment shows the point on the unit circle where sin(A)=1/4 in quadrant II. The x-coordinate is the cosine of the angle, about -0.97.