Chapter 12: Problem 2
Find the domain of \(\mathbf{r}(t)\) and the value of \(\mathbf{r}\left(t_{0}\right)\). $$ \mathbf{r}(t)=\left\langle\sqrt{3 t+1}, t^{2}\right\rangle ; t_{0}=1 $$
Short Answer
Expert verified
The domain of \( \mathbf{r}(t) \) is \( t \geq -\frac{1}{3} \) and \( \mathbf{r}(1) = \langle 2, 1 \rangle \).
Step by step solution
01
Identify components of \( \mathbf{r}(t) \)
The vector function \( \mathbf{r}(t) = \left\langle \sqrt{3t+1}, t^2 \right\rangle \) consists of two components: \( \sqrt{3t+1} \) and \( t^2 \).
02
Determine the domain for \( \sqrt{3t+1} \)
The expression \( \sqrt{3t+1} \) is defined when the quantity under the square root is non-negative. Thus, we need \( 3t + 1 \geq 0 \). Solve for \( t \) to find \( t \geq -\frac{1}{3} \).
03
Determine the domain for \( t^2 \)
The function \( t^2 \) is a polynomial and is defined for all real numbers. Thus, its domain is \( \mathbb{R} \).
04
Combine the domain conditions
To find the domain of \( \mathbf{r}(t) \), combine the domains of the individual components. The condition when both components are defined is \( t \geq -\frac{1}{3} \).
05
Evaluate \( \mathbf{r}(t_0) \)
To find \( \mathbf{r}(1) \), substitute \( t = 1 \) into \( \mathbf{r}(t) = \left\langle \sqrt{3t+1}, t^2 \right\rangle \). This gives \( \mathbf{r}(1) = \left\langle \sqrt{3(1)+1}, 1^2 \right\rangle = \left\langle 2, 1 \right\rangle \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Domain of a Function
The domain of a function refers to all the possible input values (usually represented as \( t \) in this context) that will produce valid outputs for a given function. For vector functions like \( \mathbf{r}(t) = \langle \sqrt{3t+1}, t^2 \rangle \), it's crucial to consider the domain of each individual component function separately before determining the domain of the entire vector function.
- For the component \( \sqrt{3t+1} \), the domain consists of all values of \( t \) for which the expression under the square root is non-negative. This ensures the square root function is defined, leading us to the condition \( 3t + 1 \geq 0 \). Solving this inequality, we find that \( t \geq -\frac{1}{3} \).
- The second component, \( t^2 \), is a polynomial function whose domain is all real numbers, \( \mathbb{R} \), because polynomials are defined for any real number.
Square Root Function
The square root function, denoted as \( \sqrt{x} \), is fundamental in mathematics, especially in calculus and algebra. It involves finding a number which, when multiplied by itself, gives the original number. In the context of vector functions, ensuring the expression inside the square root is non-negative is crucial.
- Given \( \sqrt{3t+1} \), for the square root to be defined, the expression \( 3t+1 \) must be \( \geq 0 \). This constraint limits the possible values of \( t \).
- We solve \( 3t + 1 \geq 0 \), leading us to \( t \geq -\frac{1}{3} \). This result highlights that the square root function's domain depends heavily on the non-negativity requirement.
Polynomial Function
Polynomial functions form one of the simplest yet most flexible classes of functions in mathematics. A polynomial function is expressed as a sum of terms, each consisting of a variable raised to a non-negative integer power and a coefficient. The domain of polynomial functions encompasses all real numbers.
- In our vector function \( \mathbf{r}(t) = \langle \sqrt{3t+1}, t^2 \rangle \), the second component \( t^2 \) is a polynomial function. This means it can take any real number as input without restrictions, unlike the square root component.
- Mathematically, you can express the domain of \( t^2 \) as \( \mathbb{R} \), indicating that for this component, there are no constraints on the value of \( t \).