Tag Archives: geometry

Manipulatives: Use With Caution!

Posted on May 18, 2012 by

Math manipulatives are concrete objects used as props in math education. As mere objects, they are, in and of themselves, not a bad thing. What is terrible is how they are often used in instruction.

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2012 AIME 1 Problem #12

Posted on April 15, 2012 by

I was checking out Mess or Math?’s cool blog and her latest post wonders whether problem 12 on the 2012 AIME 1 has a simple solution. Simple is a subjective term. The problem’s setup certainly suggests invoking things like the … Continue reading →

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Areas and Brownies

Posted on March 9, 2012 by

Recently at Girls’ Angle, we brought in a brownie and told the girls that nobody could have any until they figured out a way to dissect it so that everyone gets an equal share. I’ve done this activity before, but … Continue reading →

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Greedy Clams – Solution

Posted on November 6, 2011 by

Here’s a solution to the Greedy Clam problem that was inspired by Luyi’s “Satiated Clam” geometry problem.

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Greedy Clams

Posted on November 2, 2011 by

Here’s a problem inspired by Luyi’s “Satiated Clam” problem.  (Her problem makes me think of a clam with the biggest possible pearl inside.) The problem begins with the same setup as hers. Let ABCDEF and ABC’D’E’F’ be two regular hexagons with unit … Continue reading →

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A Problem For Circle Lovers

Posted on October 20, 2011 by

Here’s a math problem for anyone who loves circles.

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Stereographic Projection is Conformal

Posted on October 11, 2011 by

In Hana Kitasei and Tim Reckart’s animated video, Summer Vacation, Angela says that stereographic projection preserves angles. Here’s a proof.

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Hana Kitasei and Tim Reckart

Posted on October 8, 2011 by

Scramble the Angle in “Girls’ Angle,” add an “A,” and get a girl named Angela. That’s what Hana and Tim did to create Girls’ Angle’s first animated math mentor. She wears an “A” on her shirt, or is that a … Continue reading →

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3D Trapezoids

Posted on October 5, 2011 by

A few days ago, I was discussing the area formula for a trapezoid with students who had just derived it for themselves. The discussion led to a neat generalization of the trapezoid to higher dimensions different from the one that envisions the 3D … Continue reading →

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WIM Video: The Platonic Solids by Emily Peters

Posted on September 30, 2011 by

Here’s the latest WIM video, featuring MIT postdoctoral fellow Emily Peters discussing the Platonic Solids.

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