An interactive applet and associated web page that provide step-by-step animated instructions on how to measure angles using a protractor. Specifically, the applet uses a protractor to measure two angles that form a vertical pair, verifying they have the same measure.

The animation can be run either continuously like a video, or single stepped to allow classroom discussion and thought between steps.

Has link to a printable worksheet with related angle measurement problems. Suitable for class handout or homework.

Applet can be enlarged to full screen size for use with a classroom projector. After use in the classroom, student can access it again from any web browser at home or in the library with no login required.

This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.