I just posted this as a new thread on the Geometry MTBoS forum, but I wanted to put it here too. If you teach geometry, come check out the forum! Some of us are hoping it will become a nice middle ground between the speed but temporary nature of Twitter and the more formal less communication-heavy blog environment,but we need some more active users to get it to that place!
I know we have the Desmos Bank, but I sometimes find it hard to search there for things that are really geometry-centric. Desmos is still best for algebra, I know, but I prefer to use it over Geogebra with students when possible simply because I love the Activity Builder format.
So with that in mind: what are your favorite Desmos geometry activities appropriate for a high school / analytical course (some of which would fall under 8th grade standards with CCSS, thinking about transformations). I’m specifically thinking of ones that DON’T rely too much on the coordinate plane / algebra; there are lots of those available but I try not to use algebraic viewpoints to introduce most geometric concepts in my geometry course; connecting to the algebra happens, but in review/homework/later, since I often see the algebraic views as a subset of the purely geometric ones.
I’ve got a few very simple ones I made:
Exploring Rigid Transformations lets students rotate, reflect, and translate polygons and discuss effect on position, size, shape, orientation
Exploring Dilations is similar, but for dilations, with specific instructions to move the point of dilation around to different spots
If you want to make your own transformation activity (maybe one with more creative technique than mine!) I also have the calculators for reflections, rotations, dilations, and translations . You can paste those links into graphs in activity builder and they will get imported!
Deriving the Equation of a Circle helps students, well, derive the equation of a circle using the Pythagorean theorem / distance formula. This one is long, but a copy could probably remove a bunch of slides if not needed. This one of course IS algebraic, breaking my own suggestion!
I also have activities for finding the circumcenter and orthocenter of a triangle algebraically, but I frankly don’t think they’re very good and there are probably better ones out there somewhere.