Write an article based on this "Pick a large number. Plug your number, which we'll call x, into this formula to calculate pi:"
The bigger the number, the more accurate your calculation will be. x * sin(180 / x). For this to work, make sure your calculator is set to Degrees. The reason this is called a Limit is because the result of it is 'limited' to pi. As you increase your number x, the result will get closer and closer to the value of pi.