Find the length of the missing side. leave your answer in simplest radical form.

Since it is a right angled triangle, Pythagorean theorem will be applied to it to calculate the hypotenuse (missing side of the triangle). 

So, we use the formula - 
hypotenuse^2 = side1^2 + side2^2
==> hypotenuse^2 = 4^2 + 3^2
==> hypotenuse^2 = 16 + 9
==> hypotenuse^2 = 25
==> hypotenuse = square root (25)
==> hypotenuse = 5

So, the final answer is --> the length of the missing side = 5