Chapter 1: Problem 10
Starting with the graph of \(y=\sqrt{x},\) the graph of \(y=1 / x,\) and the graph of \(y=\sqrt{1-x^{2}}\) (the upper unit semicircle), sketch the graph of each of the following functions: $$f(x)=4+2 \sqrt{1-(x-5)^{2} / 9}$$
Short Answer
Expert verified
The graph of \(f(x)\) is a semicircle centered at (5, 4) with horizontal radius 3 (from 2 to 8) and vertical range [4, 6].
Step by step solution
01
Understand the base graph
The base graph is given as \(y = \sqrt{1 - x^2}\), which is the upper semicircle of the unit circle. This graph includes all points \((x, y)\) where \(-1 \leq x \leq 1\) and \(0 \leq y \leq 1\).
02
Applying horizontal shift
The function \( f(x) = 4 + 2 \sqrt{1 - (x-5)^2 / 9} \) involves a shift inside the square root. This corresponds to a horizontal shift. The term \((x - 5)^2\) indicates a shift to the right by 5 units. So, the center of the semicircle is now at \(x = 5\).
03
Adjust for the horizontal stretch/compression
The given function includes a factor of \( \frac{1}{9} \) inside the square root, implying a horizontal stretch. A factor of \(1/k^2\) causes the function to stretch by a factor of \(k\). Therefore, our function has been horizontally stretched by a factor of 3, since \( \frac{1}{9} = \left(\frac{1}{3}\right)^2 \). This means the semicircle now stretches from \(x = 2\) to \(x = 8\).
04
Understand vertical stretch and shift
The function \(2 \sqrt{1 - (x-5)^2 / 9} \) applies a vertical stretch by a factor of 2. Therefore, the maximum height of the semicircle is now 2 instead of 1. Additionally, the entire graph is shifted up by 4 units, as indicated by the \(+4\) outside the radical. Thus, the range of \(f(x)\) is \([4, 6]\).
05
Sketch the graph
Incorporating all the transformations: the graph of \(f(x) = 4 + 2 \sqrt{1 - (x-5)^2 / 9}\) is a semicircle centered at \((5, 4)\) with a radius of 3 horizontally and a radius stretched to 2 vertically. It ranges from \(x = 2\) to \( x = 8 \) on the x-axis and from \(y = 4\) to \(y = 6\) on the y-axis.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Horizontal Shift
A horizontal shift in a graph involves moving every point of a function a certain distance left or right on the x-axis. It alters the position of the graph without changing its shape. Consider the expression inside a function, such as \((x - 5)\), which indicates a horizontal shift.
- If the expression is \((x - c)\), the graph moves to the right by \(c\) units.
- Conversely, \((x + c)\) shifts the graph left by \(c\) units.
Horizontal Stretch
Horizontal stretching alters the width of a graph. It makes the graph either broader or narrower without affecting its symmetry or peak height. This is determined by multiplying the x-coordinates of the graph by a certain factor.
In the function\(\sqrt{1 - (x-5)^2/9}\), the fraction \(\frac{1}{9}\) implies a horizontal stretch. Specifically:
In the function\(\sqrt{1 - (x-5)^2/9}\), the fraction \(\frac{1}{9}\) implies a horizontal stretch. Specifically:
- A term of \(\frac{1}{k^2}\) stretches the graph horizontally by a factor of \(k\).
- Thus,\(\frac{1}{9}\) indicates a stretch by a factor of 3 (since \(\left(\frac{1}{3}\right)^2 = \frac{1}{9}\)).
Vertical Stretch
Vertical stretching involves scaling a graph along the y-axis, affecting its height without altering its width. The transformation alters the y-values by multiplying them by a given factor.
In the equation \(2\sqrt{1 - (x-5)^2/9}\), the factor outside the square root, which is \(2\), indicates a vertical stretch.
In the equation \(2\sqrt{1 - (x-5)^2/9}\), the factor outside the square root, which is \(2\), indicates a vertical stretch.
- This multiplier affects the peak height of the base graph.
- In this case, the height reaches 2 rather than the original height of 1.
Vertical Shift
A vertical shift moves a graph up or down on the y-axis without altering its shape. This adjustment depends on adding or subtracting a constant to the main equation, which alters all y-values uniformly.
In the function \(4 + 2\sqrt{1 - (x-5)^2/9}\), the \(+ 4\) indicates a vertical shift.
In the function \(4 + 2\sqrt{1 - (x-5)^2/9}\), the \(+ 4\) indicates a vertical shift.
- This positive addition shifts the entire graph vertically upward by 4 units.
- Thus, every point in the semicircle moves from its original position at y = 0 to 4, and the peak moves from 2 to 6.