Hosted by The Math Forum

Problem of the Week 1136

A Square Angle

MacPoW Home ||  Forum PoWs ||  Teachers' Place ||  Student Center ||  Search MacPoW

Let ABCD be a unit square with A at the lower left, B at lower right, C at upper right, and D at upper left. From A and B, draw lines into the square making 15° angles with the base AB, and let E be their intersection point.

What is the measure of ∠CED?

Of course, an exact proof is wanted, not a numerical approximation based on trigonometry, since the latter would not be a rigorous proof.

© Copyright 2010 Stan Wagon. Reproduced with permission.

[Privacy Policy] [Terms of Use]

Home || The Math Library || Quick Reference || Search || Help 

© 1994- The Math Forum at NCTM. All rights reserved.

1 November 2010