Essentially what we want to do is we want to find the limit as theta approaches zero of f of x. And we can't just do direct substitution into, if we really take this seriously, because we're going to like, oh, well, if I try to put zero here, it says theta cannot be equal to zero. f of x is not defined at zero. This expression is defined at zero, but this tells me, well, I really shouldn't apply zero to this function. But we know that if we can find another function that is defined, that is the exact same thing as f of x, except at zero, and it is continuous at zero. And so we could say g of x is equal to one over two plus two cosine theta. Well, then we know this limit is going to be the exact same thing as the limit of g of x as theta approaches zero.