One reason that tangents are so important is that they give the slopes of straight lines. Consider the straight line drawn in the x-y coordinate plane. The point B is where the line cuts the y-axis. We can let the coordinates of B be (0,b) so that b, called the y-intercept, indicates how far above the x-axis B lies.

Why do we draw tangents?

We often need to find tangents and normals to curves when we are analysing forces acting on a moving body. A tangent to a curve is a line that touches the curve at one point and has the same slope as the curve at that point.

What does a tangent show?

In geometry, the tangent line (or simply tangent) to a plane curve at a given point is the straight line that "just touches" the curve at that point. Leibniz defined it as the line through a pair of infinitely close points on the curve.