Why is tangent called "tangent" in trigonometry? (TANTON Mathematics) @DrJamesTanton

Uploaded April 2010 | Updated September 2026, 3 weeks ago

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"?

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