Question

what is meant by tangent line​

Answer 1

tangent, in geometry, the tangent line to a curve at a point is that straight line that best approximates (or “clings to”) the curve near that point. It may be considered the limiting position of straight lines passing through the given point and a nearby point of the curve as the second point approaches the first.

Answer 2

Answer:

A line that just touches a curve at a point, matching the curve's slope there.

(From the Latin tangens touching, like in the word "tangible".)

At left is a tangent to a general curve.