Answer:
The definition of a complementary angle states that it is a complementary angle is basically when two angles add up to 90 degrees. Regardless of if the two angles are right angles or not, when formed together to make a right triangle, the two angles will both add up to 90 degrees whenever the two are said to form a complementary angle.
Also, the sine and the cosine ratios both use the hypotenuse, but the sine uses the opposite angle in its ratio, and the cosine uses the adjacent angle in ratio.
Hope this helps.