#### Answer

$\sqrt 33$

#### Work Step by Step

The Pythagorean Theorem says that $(leg_{1}) ^{2}$+$(leg_{2})^{2}$=$hypotenuse^{2}$.
This formula is more commonly referred to as $a^{2}$+$b^{2}$=$c^{2}$
You are given the lengths of one leg as 4 and the length of the hypotenuse as 7. Substitute 4 in for a and 7 in for c.
$a^{2}$+$b^{2}$=$c^{2}$
$4^{2}$+$b^{2}$=$7^{2}$
16+$b^{2}$=49
Subtract 16 from both sides
$b^{2}$=33
Take the square root of both sides to find the length of the missing side.
b=$\sqrt 33$