Chapter 12: Problem 6
Evaluate the integrals. $$\int_{0}^{1}\left[\frac{2}{\sqrt{1-t^{2}}} \mathbf{i}+\frac{\sqrt{3}}{1+t^{2}} \mathbf{k}\right] d t$$
Short Answer
Expert verified
The integral evaluates to \( \pi \mathbf{i} + \frac{\pi \sqrt{3}}{4} \mathbf{k} \).
Step by step solution
01
Identify the Vectors
The integral separates into two distinct components: \(\int_{0}^{1} \frac{2}{\sqrt{1-t^{2}}} \mathbf{i} \, dt\) and \(\int_{0}^{1} \frac{\sqrt{3}}{1+t^{2}} \mathbf{k} \, dt\). We will evaluate each integral separately, focusing first on the component along the \(\mathbf{i}\)-direction.
02
Evaluate the Integral for \(\mathbf{i}\) Component
To integrate \(\int_{0}^{1} \frac{2}{\sqrt{1-t^{2}}} \, dt\), note that this is the integral of the derivative of the arcsine function. Thus, this integral becomes: \[\int_{0}^{1} \frac{2}{\sqrt{1-t^{2}}} \, dt = 2\sin^{-1}(t) \Big|_{0}^{1}\]Calculating at the bounds, we find:\[2\left(\frac{\pi}{2} - 0\right) = \pi.\]
03
Evaluate the Integral for \(\mathbf{k}\) Component
Next, consider \(\int_{0}^{1} \frac{\sqrt{3}}{1+t^{2}} \, dt\). Recognize this as the integral of the derivative of the arctangent function:\[\int_{0}^{1} \frac{\sqrt{3}}{1+t^{2}} \, dt = \sqrt{3}\tan^{-1}(t) \Big|_{0}^{1}\]Evaluating the function at the limits gives:\[\sqrt{3}\left(\frac{\pi}{4} - 0\right) = \frac{\pi \sqrt{3}}{4}.\]
04
Combine the Results
Combine the results for the two components:- The \(\mathbf{i}\)-direction contributes \(\pi \mathbf{i}\).- The \(\mathbf{k}\)-direction contributes \(\frac{\pi \sqrt{3}}{4} \mathbf{k}\).Thus, the evaluated integral is:\[ \pi \mathbf{i} + \frac{\pi \sqrt{3}}{4} \mathbf{k}. \]
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Definite Integrals
Definite integrals are a fundamental concept in calculus, used to find the area under a curve between two specified limits. In our example, we work with the definite integral from 0 to 1.
- The core idea is to compute the integral of a function over a specific interval.
- Integrals can represent different quantities, such as areas, volumes, and other cumulative measures.
Arcsine Function
The arcsine function is the inverse of the sine function, represented as \( \sin^{-1}(x) \). It calculates the angle whose sine is x.
- The derivative of arcsine, \( \frac{d}{dt}\left(\sin^{-1}(t)\right) = \frac{1}{\sqrt{1-t^{2}}} \), is useful in integral problems.
- For the integral \( \int \frac{1}{\sqrt{1-t^{2}}} \), it translates to \( \sin^{-1}(t) \).
Arctangent Function
The arctangent function is the inverse of the tangent function, denoted as \( \tan^{-1}(x) \), and provides the angle whose tangent is x.
- The derivative of arctangent, \( \frac{d}{dt}\left(\tan^{-1}(t)\right) = \frac{1}{1+t^{2}} \), assists in solving integrals.
- When dealing with \( \int \frac{1}{1+t^{2}} \), it naturally integrates to \( \tan^{-1}(t) \).
Integral Evaluation
Integral evaluation is the process of computing the value of an integral, often with specific boundaries or limits.
- Evaluating an integral can involve recognizing standard forms, such as arcsine or arctangent, to simplify the computation.
- The final result may involve combining the computed results of multiple integrals.