By the complementary angle relationship for sine and cosine,
sin(x°)=cos(90°−x°).
Therefore,
cos(90°−x°)= .
Either the fraction
or its decimal equivalent, 0.8, may be gridded as the correct answer
Alternatively, one can construct a right triangle that has an angle of measure
x° such that
sin(x°)=,
as shown in the figure below,
where
sin(x°) is equal to the ratio of the opposite side to the hypotenuse, or
Since two of the angles of the triangle are of measure x° and 90°, the third angle must have the measure
180°−90°−x°=90°−x°.
From the figure,
cos(90°−x°), which is equal to the ratio of the adjacent side to the hypotenuse, is also
.