A ball is thrown across a playing field from a height of h=5ft above the ground at an angle of 45 degrees to the horizontal at the speed of 20ft/s. It ca be deduced from physical principles that the path of the ball is modeled by the function

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?