Ali R. Amir-Moéz

Invariance of Circle Product

tallR =Vb2+c2-ad Proof is given in [1l. There are a few interesting and peculier things to observe. In case a real circle is chosen the norm is positive and for R = 0 we have zero norm. It is easy to show that the zero norm implies R = 0. Thus the norm is zero if and only if R = 0, i. e., the points of the plane have zero norm. Even though later we use an imaginary circle to discuss some properties of circle product we shall not go into discussion of imaginary

Teaching Trigonometry Through Vectors

Edited by Joseph Seidlin and C. N. Shu-ster This department is devoted to the teaching of mathematics. Thus articles on methodology, exposition, curriculum, tests and measurements, and any other topic related to teaching, are invited. Papers on any subject in which you, as a teacher, are interested, or questions which you would like others to discuss, should be sent to Joseph Seidlin, Alfred University, Alfred, New York. TEACHING TRIGONOMETRY THROUGH VECTORS