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.
(4r/√5)^2 = (r√2)^2 + (√10)^2 - 2(r√2)(√10)cos(135° - θ), θ = arctan(2) - 45°
Natural Language
Math Input
Extended Keyboard
Examples
Upload
Random