15-75-90 on the quarter circle
I just saw a nice visual proof of the ratios for the 15-75-90 on the internet via @ilarrosac. This one works via symmetry and the Pythagorean theorem.
15-75-90
15-75-90 Some interesting relations fall out
I’m going to do a small dive here on another 15-70-90 problem from @_eylem_99. Unlike normal I’m going to skip most of the problem solving process and inste...
15-75-90 problem meets an old friend or two
The theme of this post is connections. We’re going to start with a problem that suggests another few I’ve talked about before and I promise a 15-75-90 connec...
15-75-90 Alternate Forms
Its been a while since I’ve talked about one of my favorite triangles the 15-75-90. So here’s a short post on a new detail that I realized about them the oth...
Revisiting the 15-75-90
[This is an old post I kept around which seems appropriate to publish today before AMC 8 (which unfortunately makes for poor blogging fodder)]
And yet more 15-75-90 fun
Continuing on the theme of 15-75-90 triangles (See: Last time and First Time) several interesting riffs on 15-75-90’s in a box have come up recently.
15 - 75 Triangle Redux
I came up with this problem after looking at the original one from @five_triangles (Find the area of the trapezoid ABCD) That’s a lot of fun but along the way…