If sin 
calculate Cos A and tan A
Let ΔABC be a right-angled triangle, right-angled at point B
Given that,
Sin A = 
Let BC be 3k. Therefore, AC will be 4k, where k is a positive integer.
Applying Pythagoras theorem in ΔABC, we obtain
AC2 = AB2 + BC2
(4k)2 = AB2 + (3k)2
16k2 - 9k2 = AB2
7k2 = AB2
AB = 
k
Cos A = 
= 
= 
Tan A = 
= 
= 
30