Uh oh! Wolfram|Alpha doesn't run without JavaScript.
Please enable JavaScript. If you don't know how, you can find instructions
here
.
Once you've done that, refresh this page to start using Wolfram|Alpha.
x=(D^2/4+d^2/4+b^2/4-D*d/2*cos(4*pi*k/n))^0.5
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random