Triangles

Well, I definitely know about senior moments.

Triangles all have (at least?) four centers defined by the points at which the angle bisectors, the medians, the side bisectors, and the heights cross. One might wonder if any of the centers define interesting triangles.

scalene, right-angle, equilateral, and isoceles. so four triangles.

Do you think that right isosceles, acute isosceles, and obuse isosceles might be three categories of triangles?

Here's a site that will entertain you with math:
look for the Triangles!

7 or 6 it depends

My granddaughter, who studied geometry last year, says that there are two kinds of triangles, regular and irregular. There is one kind of regular triangle and six kinds of irregular triangles. One might apply the same argument to quadrilaterals. There is one kind of regular quadrilateral. The two kinds of irregular quadrilaterals could be convex and concave. The convex could include parallelogram, rhombus, rectangle, and trapezoid. The convex forms may not have names.

Polygons with more than four sides tend to not have names. I can think of three that have names of sorts, the concave decagon that is a five pointed star the United States flag, and the concave dodecagon that is the six pointed star on the Israeli flag. The Australian flag has fourteen sided concave polygons which I suppose are seven pointed stars.