Elementary School Resource

Obtuse Angles by Math Open Reference

This interactive web-based resource demonstrates obtuse angles (those between 90 and 180 degrees). The web page presents an angle (initially obtuse) that the user can adjust by dragging the endpoints of the line segments forming the angle. As it changes, it shows the angle measure and a message that indicates which type of angle it is. The message and angle measures can be turned off to facilitate classroom discussion. The text on the page has links to other related pages defining each angle type in depth.

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

Related NY State Academic Standards: 4.G.1!

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