So how do I think about where that particle changes direction? Well, you're going to change direction if your velocity is at zero, and right before that, your velocity was positive, and then right after that, your velocity is negative, or the other way around. Right before that, your velocity was negative, and then your velocity right after that is positive. So we just have to figure out when does v of t equal zero. So let's just say two sine of e to the t over four plus one is equal to zero, and there's multiple ways you can solve this, but because we're allowed to use a calculator, we might as well do that. So we hit Math, and then we hit B right over there. I'll just hit Enter.