Try this
Adjust the

angle below by dragging the orange dot at A and see how the angle

∠ABC behaves.
Note that it is obtuse for all angles greater than 90° and less than 180°

**While you are here..**
... I have a small favor to ask. Over the years we have used advertising to support the site so it can remain free for everyone.
However, advertising revenue is falling and I have always hated the ads. So, would you go to Patreon and become a patron of the site?
*When we reach the goal I will remove all advertising from the site.*

It only takes a minute and any amount would be greatly appreciated.
Thank you for considering it! * – John Page*

Become a patron of the site at patreon.com/mathopenref

(C) 2011 Copyright Math Open Reference. All rights reserved