Tangents & Normals
Secant lines, tangent lines and normal lines are straight lines that intersect a curve in different ways. A secant line is a line passing through two points of a curve. A line is considered a tangent line to a curve at a given point if it both intersects the curve at that point and its slope matches the instantaneous slope of the curve at that point. On a differentiable curve, as two points of a secant line approach each other, the secant line tends toward the tangent line. The idea of tangent lines can be extended to higher dimensions in the form of tangent planes and tangent hyperplanes. A normal line is a line that is perpendicular to the tangent line or tangent plane. Wolfram|Alpha can help easily find the equations of secants, tangents and normals to a curve or a surface.
Find a secant line to a curve.
Find the secant to the graph of a function through two points:
Calculate the slope of a secant line of an equation through two given points:
Find a plane that is tangent to a surface in 3D.
Find the tangent plane to a surface:
Find a tangent line to a curve.
Find the tangent to the graph of a function at a point:
Find the tangent to a curve specified by an equation:
Find a hyperplane that is tangent to an abstract surface.
Find a tangent hyperplane:
Find a line that is perpendicular to the tangent line to an equation at a point.