Well, this comes straight out of the Pythagorean identity, trig identity. This is the same thing as sine squared of x. So sine squared of x. And so I can rewrite all of this as being equal to the limit as x approaches zero. And let me rewrite this as, instead of sine squared of x, that's the same thing as sine of x times sine of x. Let me write it that way. Sine x times sine x.