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Tangent Line and Length of Curves

For curves in space we can use the vector derivative to define the tangent line.

DEFINITION

If X = F(t) is a curve in space and F'(J0) ≠ 0, the tangent line of the curve at t0 is the line with position vector F(t0) and direction vector F'(t0).

A vector parallel to F'(t0) is said to be a tangent vector of the curve at t0.

Example 2: Tangent Line of a Spiral

We have seen that the direction of the vector derivative is tangent to the curve. We next discuss the length of the vector derivative.

Suppose all the derivatives dx/dt, dy/dt, and dz/dt are continuous on an interval a ≤ t ≤ b. Recall that in two dimensions the length of the curve is defined as the integral

10_vectors-227.gif

The length of a curve in space is defined in a similar way,

10_vectors-228.gif

Example 3: Length of a Helix


Last Update: 2006-11-05