Chapter 9: Problem 12
Find the vector function that describes the curve \(C\) of intersection between the given surfaces. Sketch the curve \(C\). Use the indicated parameter. $$ x^{2}+y^{2}-z^{2}=1, y=2 x ; x=t $$
Short Answer
Expert verified
The vector function is \( \mathbf{r}(t) = \langle t, 2t, \pm \sqrt{5t^2 - 1} \rangle \).
Step by step solution
01
Analyze the given surfaces
We have two surfaces: a hyperboloid given by the equation \( x^2 + y^2 - z^2 = 1 \) and a plane given by the equation \( y = 2x \). Our goal is to find the curve of intersection between these two surfaces.
02
Substitute for the plane equation
Since the plane equation is \( y = 2x \), we substitute \( y = 2x \) into the hyperboloid equation. This gives us \( x^2 + (2x)^2 - z^2 = 1 \).
03
Simplify the hyperboloid equation
Substituting \( y = 2x \) into the hyperboloid equation results in: \[ x^2 + 4x^2 - z^2 = 1 \]. Simplifying this, we have: \[ 5x^2 - z^2 = 1 \].
04
Express variables in terms of the parameter
Given that \( x = t \), substitute \( x = t \) into the equation \( 5x^2 - z^2 = 1 \). We have:\[ 5t^2 - z^2 = 1 \]. This simplifies to \( z^2 = 5t^2 - 1 \), and therefore \( z = \pm \sqrt{5t^2 - 1} \).
05
Write the vector function
The position vector function describing the curve \( C \) is \( \mathbf{r}(t) = \langle t, 2t, \pm \sqrt{5t^2 - 1} \rangle \). This expression encompasses both branches of the intersection curve in the given parameter \( t \).
06
Sketch the curve
For a sketch, plot the vector function \( \mathbf{r}(t) \). It represents a curve having its projection as a straight line in the \( xy \)-plane (since \( y = 2x \)) and a hyperbolic component in the \( z \)-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding Hyperboloids
A hyperboloid is an interesting and significant surface in the realm of three-dimensional geometry. The equation associated with a hyperboloid is generally of the form \(x^2 + y^2 - z^2 = 1\) or similar variants. It consists of two types: a hyperboloid of one sheet and a hyperboloid of two sheets.
In our context, the hyperboloid given by \(x^2 + y^2 - z^2 = 1\) is known as a hyperboloid of one sheet.
In our context, the hyperboloid given by \(x^2 + y^2 - z^2 = 1\) is known as a hyperboloid of one sheet.
- Its key feature is that for any fixed value of \(z\), the cross-sections are circles.
- It resembles a cooling tower or a smooth hourglass shape.
- Hyperboloids have a unique characteristic of having straight lines that lie entirely on the surface.
Exploring the Curve of Intersection
The curve of intersection is where two surfaces meet in three-dimensional space. In this exercise, the surfaces are a hyperboloid and a plane.
This curve often reflects both shapes' characteristics and can be an intriguing geometrical entity.
This curve often reflects both shapes' characteristics and can be an intriguing geometrical entity.
- For the surfaces \(x^2 + y^2 - z^2 = 1\) and \(y = 2x\), the intersection is a curve where both equations hold true simultaneously.
- Substituting \(y = 2x\) into the hyperboloid simplifies it significantly, allowing us to describe the curve more easily.
- The resulting curve appears as a twisted path extending through space, maintaining the planar relationship \(y = 2x\).
Understanding Vector Functions
Vector functions are vital in representing curves in space. They utilize vectors to map from a parameter (usually \(t\)) to points on the curve.
- A vector function, like \(\mathbf{r}(t) = \langle t, 2t, \pm \sqrt{5t^2 - 1} \rangle \), provides each point's coordinate on the curve.
- It allows us to express the curve parametrically using \(t\) as a simple input, yielding a range of coordinates that describe the path.
- This transformation helps identify specific points or segments of the curve by varying \(t\).
Decoding Parametric Equations
Parametric equations define a curve by expressing each coordinate as a separate function of an independent parameter, usually \(t\).
- In the vector function \(\mathbf{r}(t)\), each component (\(x\), \(y\), and \(z\)) is given as a function of \(t\).
- This approach allows the curve to be described in terms of a single parameter, which can simplify calculations and visualizations.
- By using parametric equations, we have the freedom to consider multiple values for \(z\) simultaneously, thereby encompassing variations within the solution.