This script make the nice environment of calculate circles for console of the developer tools.
How to use:
If you use this userscript, you need open console of developer tools.
How to open the console:
Press Control + Shift + C. (if you use Mac, press Command + Option + C.)
Click "Console".
Type codes to the console.
If you want to calculate area of the circle, type "circleAreaCalculater();". (type radius of the circle to the brackets.)
If you want to calculate circumferential length of the circle, type "circumferentialLengthCalculater();". (type diameter of the circle to the brackets.)