Now, it's easy to figure out an expression for the area of this square in terms of x. But let's think about what the area of an equilateral triangle might be as a function of the length of its sides. So let me do a little bit of an aside right over here. So let's say we have an equilateral triangle just like that. And its sides are length s, s, and s. Now, we know that the area of a triangle is 1 half times the base times the height. So in this case, the height we could consider to be an altitude. If we were to drop an altitude just like this, this length right over here, this is the height.