Answer:
c = 5√5
Step-by-step explanation:
When we have a right triangle, there is a property about its measurements that is <em>always</em> true, and its called the "Pythagorean Theorem"
First, let's understand the basic terms we use to describe the sides of a triangle:
we can call one leg "a", the other leg "b" and the slanted side "c"
("c" is also called the hypotenuse--and it's always opposite the 90-degree angle)
the pythagorean theorem:
a² + b² = c²
here, our "a" is 5, our "b" is 10 {and we don't know what c is}
let's try plugging these values into our formula:
a² + b² = c²
5² + 10² = c²
25 + 100 = c²
125 = c²
now, we know what c² is--but we want to know c,
so we must take the square root of both sides
√125 = √c²
√125 = c
now, while √125 <em>is </em>our answer, we can simplify further!
this is because 125 can be made up of 5 · 25
so, 
and

we can take out the square root of 25 (5):

we write this as such: 
so, in simplest radical form, c = 5√5
(√125)
hope this helps!! have a lovely day :)