Answer:
3
Step-by-step explanation:
Easy pythagorean theorum question.
The law states that "A squared plus B squared, equals C squared."
A and B are the two sides that border the 90 degree mark.
C is the hypotenuse or the longest side/diagonal.
Since we know C and A (I chose to use A because why not) we can fill in the equation with what we know
2^2 + ?^2 =
So
4 + ?^2 =
Since the 13 is already squared in side of a root, it stays as 13
4 + x^2 = 13
4 - 4 + x^2 = 13 - 4
x^2 = 9
x^2 root = root of 9
x = 3
The missing side is 3.
Or you could use an online calculator xD