Chapter 3: Problem 18
Exer. 13-26: Sketch, on the same coordinate plane, the graphs of \(f\) for the given values of \(c\). (Make use of symmetry, shifting, stretching, compressing, or reflecting.) $$ f(x)=\sqrt{9-x^{2}}+c ; \quad c=-3,0,2 $$
Short Answer
Expert verified
Plot three semicircles with centers at (0,-3), (0,0), and (0,2).
Step by step solution
01
Understand the Basic Function
The function given is \( f(x) = \sqrt{9 - x^2} + c \). The term \( \sqrt{9 - x^2} \) represents a semicircle centered at the origin (0,0) with radius 3. Without any constant \( c \), the graph is a semicircle on the upper half-plane.
02
Analyze the Effect of c on the Graph
The constant \( c \) acts as a vertical shift for the semicircle. If \( c > 0 \), the semicircle shifts upwards by \( c \) units. If \( c < 0 \), the semicircle shifts downwards by \( |c| \) units. For \( c = 0 \), there is no vertical shift.
03
Draw the Graph for c = -3
For \( c = -3 \), the graph is a downwards shift of the semicircle centered at (0,0) by 3 units. Therefore, the center of the semicircle will be \((0, -3)\). The semicircle will still have a radius of 3.
04
Draw the Graph for c = 0
For \( c = 0 \), the graph remains the original semicircle with its center at the origin \((0,0)\). It is a semicircle on the upper half-plane, with a radius of 3.
05
Draw the Graph for c = 2
For \( c = 2 \), the graph shifts the semicircle upwards by 2 units. The center of the semicircle is now at \((0, 2)\), with the semicircle still having a radius of 3.
06
Combine the Graphs on One Plane
Place all three semicircles on the same coordinate plane. Each has a radius of 3 but are vertically shifted based on the value of \( c \). For \( c = -3 \), the semicircle is centered at \((0, -3)\). For \( c = 0 \), it is at the origin \((0,0)\). For \( c = 2 \), it is at \((0, 2)\). Ensure accurate plotting so that the symmetrical nature of the semicircles is clear.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Vertical Shifts
In graph transformations, vertical shifts play a significant role in moving the entire graph up or down on the coordinate plane. This movement is controlled by adding or subtracting a constant value from the function. In the expression given, namely \(f(x) = \sqrt{9 - x^2} + c\), the constant \(c\) determines how much and in which direction the graph is shifted vertically.
- If \(c > 0\), every point on the semicircle will move up by \(c\) units. This is an upward shift.
- For \(c < 0\), the entire graph shifts down, with each point moving \(|c|\) units lower.
- When \(c = 0\), no vertical shift occurs, and the graph remains in its original position.
Semicircle Graph
Graphs of semicircles are frequently encountered in mathematical problems involving geometric shapes. A semicircle graph represents half of a circle and is defined by equations involving square roots, as seen in \(f(x) = \sqrt{9-x^{2}}\).
- This particular equation denotes a semicircle because it features the square root of an expression similar to the equation of a circle. The square root limits the graph to the upper half-plane.
- The center of the semicircle is at the origin, (0, 0), before any transformation is applied.
- All points on this graph are equidistant from the origin, forming a perfect half-dome shape that stops at the x-axis.
Radius of a Semicircle
The radius in a circle or semicircle remains a crucial measurement that determines the size of the graph. For the function \(f(x)=\sqrt{9-x^2}\), the number under the square root, 9, directly implies a radius of 3.
- The reason is that the term \(9-x^2\) resembles the format \(r^2\) of a circle's equation \(x^2 + y^2 = r^2\). Here \(r = 3\) since \(\sqrt{9} = 3\).
- The radius determines the maximum distance any point on the semicircle can have from its center. In this case, this radius ensures that the graph arch reaches x-coordinates -3 to 3.
- Consistent radius across all transformation maintains the general size and shape of semicircles, regardless of shifting.
Coordinate Plane Plotting
Plotting on a coordinate plane requires an understanding of both horizontal and vertical axes. To plot a function like \(f(x) = \sqrt{9-x^2}+c\), follow these steps:
- Identify the center of the semicircle, which initially is at \(0, 0\).
- Considering vertical shifts: move this center up or down based on the value of \(c\).
- Plot the endpoints of the semicircle along the x-axis, ensuring they respect the radius. For a radius of 3, these endpoints would be at \(-3, 3\).
- Draw the semicircle forming an arc from the left endpoint to the right, ensuring symmetry.