Please help due NOW PLEASE HELP

For the equations below which statement is true ?

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?

The angle of elevation from point a to the top of the cliff is 38 degrees. if point a is 80 feet from the base of the cliff , how high is the cliff ?