The given triangle is a right angle .
In this triangle for angle A side AC is adjacent side ,BC is opposite side and AB is hypotenuse.
Sin of any angle is the ratio of opposite and hypotenuse .
[tex] sin=\frac{opposite}{hypotenuse} [/tex]
Substituting the values of opposite and hypotenuse
SinA=[tex] \frac{12}{37} [/tex]
