Chapter 14: Problem 26
Find the limits in Exercises \(21-26\). $$ \lim _{P \rightarrow(0,-2,0)} \ln \sqrt{x^{2}+y^{2}+z^{2}} $$
Short Answer
Expert verified
The limit is \( \ln 2 \).
Step by step solution
01
Identify the Limit Expression
We are given the expression \( \lim_{P \rightarrow (0,-2,0)} \ln \sqrt{x^{2}+y^{2}+z^{2}} \). Our goal is to evaluate the limit as the point \( (x,y,z) \) approaches \( (0,-2,0) \).
02
Understand the Inside Function
The expression inside the logarithm is \( \sqrt{x^2 + y^2 + z^2} \). This represents the Euclidean distance from the point \((x, y, z)\) to the origin \((0,0,0)\). As \((x,y,z)\) approaches \((0,-2,0)\), this expression becomes \( \sqrt{0^2 + (-2)^2 + 0^2} \).
03
Simplify the Distance Formula
Calculate \( \sqrt{x^2 + y^2 + z^2} \) at the point \((0,-2,0)\): \( \sqrt{0^2 + (-2)^2 + 0^2} = \sqrt{4} = 2 \).
04
Evaluate the Limit
Substitute the simplified expression into the limit: \( \lim_{P \rightarrow (0,-2,0)} \ln \sqrt{x^2 + y^2 + z^2} = \ln 2 \). This is because as \(P\) approaches \((0, -2, 0)\), the expression inside the logarithm approaches 2.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Euclidean Distance
In our exercise, we encounter the term \(\sqrt{x^2 + y^2 + z^2}\), which is the formula for calculating Euclidean distance in three-dimensional space. Euclidean distance measures how far two points are from each other.Let's break down the formula:- **\(x^2\):** the square of the difference in the x-coordinates of two points.- **\(y^2\):** the square of the difference in the y-coordinates.- **\(z^2\):** the square of the difference in the z-coordinates.Combine them: \(\sqrt{(x_2-x_1)^2 + (y_2-y_1)^2 + (z_2-z_1)^2}\) gives the straight-line distance from one point to another in space.For instance, the distance from the origin \((0,0,0)\) to a point \((3,4,0)\) is calculated as:- \(\sqrt{3^2 + 4^2} = \sqrt{9 + 16} = 5\).Understanding Euclidean distance helps in visualizing how far the point \((x,y,z)\) is from a given point, like \((0,-2,0)\) in your exercise.
Logarithmic Functions
The function \(\ln(\sqrt{x^2 + y^2 + z^2})\) involves a natural logarithm (\(\ln\)). Logarithms are used to scale numbers, making it easier to work with large values or multiplicative relationships.Logarithms have key properties:
- **\(\ln(1) = 0\)**: The log of 1 is always zero regardless of the base.
- **\(\ln(ab) = \ln(a) + \ln(b)\)**: The log of a product is the sum of logs.
- **\(\ln(a^b) = b \cdot \ln(a)\)**: You can move the exponent out front as a multiplier.
Limit Evaluation
Evaluating limits helps in understanding the behavior of functions as values approach a certain point. In your exercise, we evaluate the limit of the expression \(\ln\sqrt{x^2+y^2+z^2}\) as \((x,y,z)\) heads to \((0,-2,0)\).Here's a simple approach:- **Identify the limit point**: Ensure clarity in what point the variables are approaching.- **Substitute the values**: Compute the inner expression directly if possible.For instance, with \(\sqrt{0^2 + (-2)^2 + 0^2} = 2\), the natural log gives us \(\ln(2)\).When you're dealing with limits in three dimensions, visualize it as a point moving through space towards the specific target coordinates. It's about focusing on what happens "ongoing" behaviors – How does the function change or stabilize as you near a certain point?
Three-Dimensional Space
Three-dimensional space involves dimensions like width, depth, and height, unlike the usual two dimensions. Every position in this space is represented by a triplet \((x, y, z)\).To imagine 3D space, think about a cube:
- **x-axis:** left to right direction.
- **y-axis:** front to back direction.
- **z-axis:** top to bottom direction.