lift hill of a roller coaster that models the equation , where y is the height and x is the length from the start of the lift hill. Using this model, how far from the start of the lift hill does the ride reach a height of 343 meters?

You are standing next to a really big circular lake. you want to measure the diameter of the lake, but you don't want to have to swim across with a measuring tape! you decide to walk around the perimeter of the lake and measure its circumference, and find that it's 400\pi\text{ m}400? m. what is the diameter dd of the lake?