Expected value of the area of square

[Glass]

Homework Statement

Given a square with side lengths X, where X is a random variable with some probability density function (the actual pdf is not important for my question). Why isn't the expected value of the area = E[X]^2 = E[X^2]?

Homework Equations

The Attempt at a Solution

Intuitively I would think, if I can find the expected value of one of the sides, I can get the expected value of the area by squaring it.
On the other hand, I am well aware that E[X]^2 != E[X^2] in the general case, and this is indeed a general case (with some geometric interpretation).

 

[Glass]

Wait nevermind, I got it.