Geoboard Math for Teachers
D. Geoboard image
2S4 worksheet: Pinboard Triangles and Quadrilaterals
3S2 nrich〈Name That Triangle〉
3S2 NCTM〈Triangle Classification〉
4S2 Dissection of an isosceles trapezium
5M1 Pick's Rule 1997/04/11
5M1 Alex CHIK〈Pick's Formula〉