I’ve talked before about providing students an opportunity to **look for and make use of structure** while trying to prove the Triangle Sum Theorem. This summer I ran across… 1,073 more words

## Tags » Geometry

#### Sum of Angles in a Triangle

#### Parallel Lines Never Meet... or Do They?

Got an idea for Geometry. So far it seems like my kids have significant prior experience with parallel lines, so after introducing the parallel lines postulate, I’m going to talk about non-Euclidean geometry, namely spherical geometry. 153 more words

#### Transversals, Parallel Lines and Discovering Angle Properties

The #MTBoS is a wonderful place. Sometimes the only problem is deciding which awesome activity I will do, since I don’t have time to do them all! 712 more words

#### Tangent II

I had a thought about another way to approach that ellipse and circles problem and thought I’d try it on a generalization. Suppose the circle is of arbitrary radius and sitting at an arbitrary point? 635 more words

#### An elliptical tangent

Another oddball ellipse topic: Let’s suppose you have two unit circles (*r*=1) adjacent, i.e. tangent, to one another, and you want to draw an ellipse that contains them. 835 more words

#### Dividing ellipses

Yeah, I’m still around.

I’ve been thinking about ellipses lately. For Reasons.

Here’s a sort of silly question. Suppose I gave you a circle and asked you to mark four points on it, evenly spaced. 1,275 more words

#### Origami Regular Octagon

We folded a square piece of paper as described in the Illustrative Mathematics task, Origami Regular Octagon. I didn’t want students to know ahead of time that they were creating an octagon, so I changed the wording a bit. 587 more words