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”?


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