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.
证明若 A 上三角且 B 上三角，则 AB 上三角。
证明若 A 上三角且 B 上三角，则 AB 上三角。
Natural Language
Math Input
Extended Keyboard
