Mathematics| is a series of professional quality computer animated videotapes containing modules on various topics in basic mathematics. This project will produce six modules on high school geometry for use in classrooms and learning centers. Each module tape will be about 20 minutes long and will be accompanied by student workbooks and teacher manuals. The modules are intended to be easily integrated into current curricula. The tapes are designed to encourage interaction between the video tape, teacher, and students. This is done by structuring each tape into small capsules, which are identified by number titles keyed to the student workbooks, permitting the teacher to stop the tape at the end of each capsule to allow discussion by the students. The tapes will be produced by the same team that created the 52 half hour episodes of "The Mechanical Universe" and the twenty minute pilot tape of "The Theorem of Pythagoras." All materials will be distributed on a nonprofit basis through a consortium of state departments of education, and through workshops and assistance from the Mathematical Association of America (MAA) and the National Council of Teachers of Mathematics (NCTM). Field testing, evaluation, and teacher training is an essential part of the proposal. High school teachers will be involved at every developmental stage, and ongoing teacher support will be arranged through the consortium.