Respuesta :

Use the Pythagorean theorem 
a
²+b²=c²
https://en.wikipedia.org/wiki/Pythagorean_theorem

your problem is: 
a = 2
b = 10 
c = ? 

2²+10²= c²
c² = 4+100
c² = 102
√102 = 10.0995049384
c = 10.0995049384

You're welcome ;)