Several times a week I walk by a metal chair that is fastened to a flat concrete slab at an outdoor bus stop here in Boulder. One day I noticed on the concrete a nice shadow image of the woven metal seat of the chair (Fig. 1). The seat and back of the chair are formed from 3.8-cm wide strips of metal spaced 3.8 cm apart. The seat is about 39 cm…

Presents a geometric discovery involving the use of a trapezoid as a base for a pyramid. Includes reproducible student worksheet to be used as a group-discovery exercise. (MKR)

Discusses a conjecture of a ninth-grade student that extended a geometry theorem about trisecting sides of a triangle. Presents a proof and extensions. (MKR)

Discusses assumptions implicit in any system of measurement. Describes a three-rectangle problem designed to help children explore additivity of areas and relationships between area and shape. Suggests ideas for action research. (FDR)

Described is a method of teaching geometric constructions. The method relates five basic constructions to the properties of a rhombus. (RH)

This essay contains some reflections and questions arising from encounters with the text of Euclid's Elements. The reflections arise out of the teaching of a course in Euclidean and non-Euclidean geometry to undergraduates. It is concluded that teachers of such courses should read Euclid and ask questions, then teach a course on Euclid and later…

Cooperative groups were given transparencies of eight regular inscribed polygons and overlays of corresponding circumscribed polygons and were asked to find the perimeters and ratios of perimeter to diameter. Transparencies give students a graphic illustration of limits. Includes reproducible worksheet. (NI)

Using sequential chains of regular n-gons in a row with one side touching, as for example, one triangle, two triangles, three triangles, and so on, students graph the length of the perimeter versus the number of n-gons and determine the functional relationship for different values of n. (MKR)

Presents results from research aimed to design and experiment with a set of units for teaching plane isometries in grades 3 through 12 and applies the van Hiele model of geometric reasoning to isometries. Includes a table of characteristics of teaching objectives for the van Hiele Levels in Isometries. (MKR)

Describes three activities in discrete mathematics that involve coloring geometric objects: counting colored regions of overlapping simple closed curves, counting colored triangulations of polygons, and determining the number of colors required to paint the plane so that no two points one inch apart are the same color. (MKR)

Includes lesson plans and worksheets that deal with transformational geometry, specifically reflections. The lesson for grades three to four focuses on angles of incidence and reflection and that for grades five to six involves mirror images. (MKR)

Investigates the idea of the center of mass of a polygon and illustrates centroids of polygons. Connects physics, mathematics, and technology to produces results that serve to generalize the notion of centroid to polygons other than triangles. (KHR)

Presents an activity in which students use geometric figures, rep-tiles, to design a tile floor. Rep-tiles are geometric figures of which copies can fit together to form a larger similar figure. Includes reproducible student worksheet. (MKR)

This Missouri Vocational Instruction Management System instructor's drafting guide has been keyed to the drafting competency profile developed by state industry and education professionals. The guide contains a cross-reference table of instructional materials. Three units cover related views and descriptive geometry: (1) auxiliary views and…

Presents five worksheets that contain hands-on geometry activities dealing with the ideas of quadrilateral, trapezoid, parallelogram, isosceles, kite, axis of symmetry, and rhombus. (MKR)