The cross product of two vectors is important concept which is applied in solving many problems when using the spatial coordinate method. By applying the Theory of Didactical Situations in Mathematics, the authors designed teaching situation that they call “the cross product of two vectors concept” in which students learn through situations that involve action, communication and validation. | JOURNAL OF SCIENCE OF HNUE Vol. 57 No. 1 pp. 3-7 DESIGNING A TEACHING SITUATION THE CROSS PRODUCT OF TWO VECTORS CONCEPT Geometry Textbook for 12nd Grade Chapter 3 Lesson 2 Bui Van Nghi Hanoi National University of Education Nguyen Tien Trung University of Education Publishing House HNUE Email trungnt@ Abstract. The cross product of two vectors is important concept which is applied in solving many problems when using the spatial coordinate method. By applying the Theory of Didactical Situations in Mathematics the authors designed teaching situation that they call the cross product of two vectors concept in which students learn through situations that involve action communication and validation. Keywords Theory of Didactical Situations in Mathematics cross product. 1. Introduction Making use of Theory Didactical Situations in Mathematics we can design teaching situations that will encourage active learning in students. The cross prod- uct of two vectors is a new and somewhat special concept that is used by high school mathematics teachers. This concept can be used to solve many problems that involve the spatial coordinate method. In this paper the authors describe a teaching situa- tion that they designed which makes use of the cross product concept to introduce a positive learning activity to students. 2. Content On basis of the Theory of Didactical Situations in Mathematics and other theories that involve active teaching methods 1 2 3 8 the authors designed a scenario of a teaching situation to develop the concept of cross product of two vectors. The scenario involves the following actions 3 Bui Van Nghi and Nguyen Tien Trung . Action 1 Situation of action 1 The teacher asks students to solve problem In space there exists plane ABC with A 2 1 3 B 4 0 1 C 1 1 0 . Let determine normal vector of ABC . Solution We have two vectors AB 2 1 2 AC 1 2 3 with their direc- tion parallel to a plane ABC . The two vectors AB AC are not in the same direction .
