Chapter 9: Problem 15
Sketch a contour diagram for the function with at least four labeled contours. Describe in words the con- tours and how they are spaced. \(f(x, y)=x+y\)
Short Answer
Expert verified
The contour diagram consists of parallel lines (with slope -1), equally spaced vertically by 1 unit.
Step by step solution
01
Understanding the Contour
The function given is a simple linear function: \( f(x, y) = x + y \). A contour line for \( z = c \) (where \( c \) is a constant) represents all points \((x, y)\) such that \( x + y = c \). Thus, each contour line can be represented as \( y = c - x \).
02
Identifying Contour Lines
Since the contours represent the equation \( y = c - x \), each contour is a line. To draw at least four contours, select four different constant values for \( c \). For example, let's take \( c = 1, c = 2, c = 3, c = 4 \). This gives us four lines: \( y = 1 - x \), \( y = 2 - x \), \( y = 3 - x \), and \( y = 4 - x \).
03
Drawing the Contour Lines
On a Cartesian plane, draw the four contour lines. For \( c = 1 \), the line \( y = 1 - x \) can be drawn by plotting two points such as \((0, 1)\) and \((1, 0)\), and drawing a line through them. Repeat similarly for \( c = 2 \), \( c = 3 \), and \( c = 4 \) to get respective lines \( y = 2 - x \), \( y = 3 - x \), and \( y = 4 - x \).
04
Describing the Contours
Each contour is a straight line with a negative slope of -1. As the constant \( c \), which represents the function's value, increases, the line shifts upwards parallel to the previous one. The spacing between each of the contour lines is equal because the increase in \( c \) by 1 results in a vertical shift by 1 unit parallelly upwards.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Linear Function
A linear function is one of the simplest types of functions in mathematics. It's called "linear" because its graph is a straight line. In our context, the function is defined as \( f(x, y) = x + y \). This particular linear function represents a plane in 3-dimensional space. The relationship between the inputs \( x \) and \( y \) is straightforward, as each unit increase in either \( x \) or \( y \) results in a corresponding increase in the function's value.Linear functions can be recognized by their characteristic form:
- They have constants and variables only raised to the power of one.
- They graph as straight lines on a 2D plane.
Constant Value
When we talk about a 'constant value' in the context of contour diagrams, we are referring to a fixed number that a line represents on the graph. Here, for the function \( f(x, y) = x + y \), the constant value represented by each contour line is \( c \), where \( c \) is any real number.In this scenario:
- The contour lines are the result of setting the linear function equal to these constant values.
- Each line represents the equation \( x + y = c \), which can be rewritten as \( y = c - x \).
- The constant value \( c \) dictates how the lines are spaced along the graph.
Cartesian Plane
A Cartesian plane is a two-dimensional plane defined by two perpendicular axes: the horizontal axis (x-axis) and the vertical axis (y-axis). It is used extensively in math to plot equations and graph relationships between variables.For drawing contour lines:
- The x-axis and y-axis divide the plane into four quadrants.
- Points are specified by coordinates \((x, y)\).
Contour Lines
Contour lines are lines on a graph that illustrate locations where the function holds a constant value. In the case of our problem, these contour lines result from the function \( x + y = c \).Few key points about contour lines:
- They are always straight for linear functions like \( f(x, y) = x + y \).
- Each line’s placement is determined by a different constant value \( c \).
- For this function, the lines slope downward at a constant rate because this is a simple linear relationship.