Tangent Plane

Intuitively, it seems clear that, in a plane, only one line can be tangent to a curve at a point. However, in three-dimensional space, many lines can be tangent to a given point. If these lines lie in the same plane, they determine the tangent plane at that point. A tangent plane at a regular point contains all of the lines tangent to that point. A more intuitive way to think of a tangent plane is to assume the surface is smooth at that point (no corners). Then, a tangent line to the surface at that point in any direction does not have any abrupt changes in slope because the direction changes smoothly.

Definition of Tangent Plane

Let $P_{0}=(x_{0},y_{0},z_{0})$ be a point on a surface $S$, and let $C$ be any curve passing through $P_{0}$ and lying entirely in $S$. If the tangent lines to all such curves $C$ at $P_{0}$ lie in the same plane, then this plane is called the tangent plane to $S$ at $P_{0}$.

For a tangent plane to a surface to exist at a point on that surface, it is sufficient for the function that defines the surface to be differentiable at that point, defined later in this section. We define the term tangent plane here and then explore the idea intuitively.

Equation of Tangent Plane

Let $S$ be a surface defined by a differentiable function $z=f(x,y)$, and let $P_{0}=(x_{0},y_{0})$ be a point in the domain of $f$. Then, the equation of the tangent plane to $S$ at $P_{0}$ is given by

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Resources

Videos

• Tangent planes | MIT 18.02SC Multivariable Calculus, Fall 2010

• Determining the Equation of a Tangent Plane Video by Mathispower4u 2011

• Ex 1: Find the Equation of a Tangent Plane to a Surface video by Mathispower4u 2014

• How To Find The Equation of the Normal Line-The Organic Chemistry Tutor 2014 Video by The Organic Chemistry Tutor 2014

• quation of the normal line at a point (KristaKingMath) Video by KristaKingMath 2012

• Tangent Plane Approximations Video by -patrickJMT