1. By definition, you have:
Sin(α)=Opposite/Hypotenuse
2. Then, SinA is:
SinA=BC/AC
A is the angle in the vertice "A".
BC is the opposite leg to the the angle A.
AC is the hypotenuse of the triangle.
3. By definition, you have:
Cosα=Adjacent/Hypotenuse
4. Then, CosC is:
CosC=BC/AC
C is the angle at the vertice "C".
BC is the adjacent leg to the angle C.
AC is the hypotenuse.
5. Therefore, the answer is the last option:
The equivalent to SinA is CosC
