In this section, we will learn about:
Vector functions and drawing their corresponding space curve
In general, a function is a rule that assigns to each element in the domain an element in the range.
A vector-valued function, or vector function, is simply a function whose:
§ Domain is a set of real numbers.
§ Range is a set of vectors.
We are most interested in vector functions r whose values are three-dimensional (3-D) vectors.
§ This means that, for every number t
in the domain of r, there is a unique
vector in V3 denoted by r(t).
If f(t), g(t), and h(t) are the components of
the vector r(t), then f, g, and h are real-valued functions called the component functionsof r.
Wecan write:
r(t) = ‹f(t), g(t), h(t)› = f(t) i + g(t) j + h(t) k
We usually use the letter t to denote
the independent variable because
it represents time in most applications
of vector functions.
If
then the component functions are: ![]()
By our usual convention, the domain of r consists of all values of t for which the expression for r(t) is defined.
§ The expressions t3, ln(3 – t), and are all defined when 3 – t > 0 and t ≥ 0.
§ Therefore, the domain of r is the interval [0, 3).
The limitof a vector function r is defined by taking the limits of its component functions as follows.
If r(t) = ‹f(t), g(t), h(t)›, then
provided the limits of the component functions exist.
If
, this definition is equivalent to saying that the length and direction of the vector r(t) approach the length and direction of the vector L.
Find
where ![]()
According to Definition 1, the limit of r is
the vector whose components are the limits
of the component functions of r:

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