In plane geometry, a straight line is called a tangent to a circle. If this line meets the circle at precisely one it is known as the tangent to a circle, which is presented in the diagram below on the right.
A line which cuts the circle at two distinct points is known as the secant line, and the third scenario is that a line neither touches nor cuts the circle. In the next few tutorials we shall discuss the tangent line and secant line. In calculus, the tangent to a circle is the limit of the secant of a line, because from the secant of a line one point on the circle approaches another to attain the tangent to a circle.