Why is tangent called “tangent”? (VIDEO!)

And why is secant called “secant” and cosine called co – sine? Why these names? In this video I explain the connection between the tangent of an angle and a tangent line. Ditto for the secant of an angle and a secant line.

BTW: Did you know that “sine” means “harbour” or “cove”?

Why “tangent”?

• ON-LINE SHORT COURSES!

  QUADRATICS, Permutations and Combinations, EXPLODING DOTS, and more!

  Written for educators - and their students too! - this website, slowly growing, takes all the content Tanton has developed in his books, videos, and workshops, and organizes it into short, self-contained, and complete, curriculum units proving that mathematics, at all points of the school curriculum, can be joyous, fresh, innovative, rich, deep-thinking, and devoid of any rote doing! Let's teach generations of students to be self-reliant thinkers, willing to flail and to use their common sense to "nut their way" through challenges, to assess and judge results, and to adjust actions to find success. (Great life skills!)

  CHECK OUT: www.gdaymath.com

• Books

  • Thinking Mathematics! (TEN VOLUMES)
  • Solve This: Mathematical Activities for Students and Clubs
  • Encyclopedia of Mathematics
  • Geometry I & II

• Get in touch

  Email: tanton.math@gmail.com