Chapter 11: Problem 20
Name and sketch the graph of each of the following equations in three-space. $$ z=\sqrt{x^{2}+y^{2}+1} $$
Short Answer
Expert verified
The graph is a dome-shaped surface starting at \( z = 1 \) and opening upwards, known as a paraboloid.
Step by step solution
01
Identify the Equation Type
The given equation is in the form \( z = \sqrt{x^2 + y^2 + 1} \). This equation resembles the form of a paraboloid, albeit modified due to the square root. Typically, paraboloids take the form \( z = \sqrt{x^2 + y^2} \), but here we have \(+1\) inside the square root.
02
Analyze the Shape
Since \( z = \sqrt{x^2 + y^2 + 1} \) always yields real, positive values (as square roots do), the surface remains positive along the z-axis. The term \( +1 \) results in an upward shift along the z-axis such that at \( x = 0 \) and \( y = 0 \), \( z = 1 \). This indicates a paraboloid that does not pass through the origin but rather starts from \( z = 1 \).
03
Sketch the Graph
Visualize the graph starting from the point \( (0, 0, 1) \). As \( x \) and \( y \) move away from zero, \( z \) increases due to the added distance squared, forming an upward-opening surface resembling a paraboloid dome. At every point on the surface, the value of \( z \) is determined by moving out radially in every direction from \( (0, 0, 1) \), creating a smooth surface without sharp edges.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Paraboloid
A paraboloid is a three-dimensional surface that can be generated by rotating a parabola around its axis. In simpler terms, it's like a bowl or a dome shape. Paraboloids come in two primary forms: elliptic and hyperbolic. This exercise focuses on an elliptic paraboloid, which has a convex, upward-opening shape.Imagine taking a standard parabola (like the graph of a quadratic function) and revolving it around its vertical axis. The result is a surface that extends infinitely in three dimensions.
- In affine form, a standard elliptic paraboloid equation is either:
- Vertical: \( z = x^2 + y^2 \)
- Horizontal: \( y = x^2 + z^2 \)
Square Root Function
The square root function is crucial when working with graphs involving non-linear shapes. For any positive number \( a \), \( \sqrt{a} \) gives a value that, when multiplied by itself, returns \( a \). In graphs, this function causes data points to rise sharply and then flatten as they move along the axis.In the equation \( z = \sqrt{x^2 + y^2 + 1} \), the square root provides smoothing by changing angular curves into softer arcs. This rounding is important because it adjusts how the graph can be understood—transforming a sharp parabola into a gentler, dome-like surface in the 3D space.
- Square root functions are inherently non-negative; thus, \( z \) is always positive.
- This means no negative values will exist along the \( z \)-axis, reinforcing an upward-facing graph.
- The structure \( +1 \) inside the function ensures the minimum starting point is \( z = 1 \) when \( x \) and \( y \) are zero.
Graphical Analysis
Graphical analysis helps us interpret and visualize mathematical functions into tangible shapes and forms. By effectively analyzing the given equation, we derive its geometry in a three-dimensional space, allowing us to "see" what the function represents.For the function \( z=\sqrt{x^2+y^2+1} \), the graph represents a 3D surface, which can be interpreted and analyzed like any visual data:
- The graph's vertex is at \( (0, 0, 1) \), indicating where the shape starts.
- As \( x \) and \( y \) increase, the graph opens upwards symmetrically in all directions, since the values under the square root grow larger.
- Understanding the transformation from 2D to 3D involves seeing how each point translates in each dimension.
3D Coordinate System
The 3D coordinate system is a method for locating points in three-dimensional space using three coordinates: \( x \), \( y \), and \( z \).Unlike a 2D plane (which only uses \( x \) and \( y \)), the 3D system allows for depiction of volume and depth—exceedingly important in accurately representing figures like the given paraboloid.
- Points are represented as \( (x, y, z) \).
- The positive \( z \)-axis indicates movement away from the origin "upwards," while the \( x \)-axis and \( y \)-axis are your horizontal and vertical planes.
- This system enables mathematicians and scientists to categorize objects with an accurate depiction of dimensions.