Chapter 6: Problem 53
Evaluate the definite integrals exactly \([as in \)\ln (3 \pi)]\(,\) using the Fundamental Theorem, and numerically \([\ln (3 \pi) \approx 2.243]\) $$\int_{0}^{\pi / 4} \sin x d x$$
Short Answer
Expert verified
The exact value is \( 1 - \frac{\sqrt{2}}{2} \), approximately 0.293.
Step by step solution
01
Identify the Integral Function
We are asked to solve the definite integral \( \int_{0}^{\pi / 4} \sin x \, dx \). Here, the function we need to integrate is \( \sin x \), and the limits of integration are from 0 to \( \frac{\pi}{4} \).
02
Apply the Fundamental Theorem of Calculus
According to the Fundamental Theorem of Calculus, to evaluate the definite integral \( \int_{a}^{b} f(x) \, dx \), we first find the antiderivative of \( f(x) \). The antiderivative of \( \sin x \) is \( -\cos x \).
03
Evaluate the Antiderivative at the Limits
Apply the limits of integration to the antiderivative. Substitute the upper limit \( \frac{\pi}{4} \):\[ -\cos\left(\frac{\pi}{4}\right) = -\frac{\sqrt{2}}{2} \].Substitute the lower limit 0:\[ -\cos(0) = -1 \].
04
Compute the Definite Integral
Subtract the value of the antiderivative at the lower limit from its value at the upper limit:\[ \int_{0}^{\pi / 4} \sin x \, dx = -\frac{\sqrt{2}}{2} - (-1) = 1 - \frac{\sqrt{2}}{2} \].
05
Numerical Approximation
To approximate the value numerically: Calculate \( 1 - \frac{\sqrt{2}}{2} \) using an approximate value for \( \sqrt{2} \approx 1.414 \):\[ 1 - 0.707 \approx 0.293 \].
Unlock Step-by-Step Solutions & Ace Your Exams!
-
Full Textbook Solutions
Get detailed explanations and key concepts
-
Unlimited Al creation
Al flashcards, explanations, exams and more...
-
Ads-free access
To over 500 millions flashcards
-
Money-back guarantee
We refund you if you fail your exam.
Over 30 million students worldwide already upgrade their learning with 91Ó°ÊÓ!
Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Fundamental Theorem of Calculus
The Fundamental Theorem of Calculus is a cornerstone of mathematical analysis. It links the notion of differentiation and integration, two essential concepts in calculus. This theorem asserts that if you have a continuous function \( f(x) \) on a closed interval \([a, b]\), and if \( F \) is an antiderivative of \( f \) on \([a, b]\), then:
- \( \int_{a}^{b} f(x) \, dx = F(b) - F(a) \)
Numerical Integration
Numerical integration is a method to approximate the value of a definite integral, especially when finding the exact antiderivative is complex or impossible. In our exercise, we computed the integral \( \int_{0}^{\pi/4} \, \sin x \, dx \) as \( 1 - \frac{\sqrt{2}}{2} \), which simplifies to a precise numerical value. However, it's often needed to estimate this with a numerical approach.
- Methods like the Trapezoidal rule and Simpson's rule are popular for numerical integration.
- In this case, the approximation gave us \( 0.293 \), using \( \sqrt{2} \approx 1.414 \).
Trigonometric Functions
Trigonometric functions are essential in mathematics, especially in calculus. The sine function, \( \sin x \), which appears in our integral \( \int_{0}^{\pi/4} \sin x \, dx \), is one of the primary trigonometric functions, derived from the properties of right-angled triangles.
- Trigonometric functions like sine, cosine, and tangent have periodic properties and are used to model cyclic behaviors.
- In calculus, these functions frequently appear in both derivatives and integrals, due to their repeating patterns and smooth curves.
Antiderivative
An antiderivative is a function whose derivative is the given function. In our exercise, the goal was to find the antiderivative of \( \sin x \), which is \(-\cos x\). This step is critical in applying the Fundamental Theorem of Calculus.
- The antiderivative of a function is not unique; it includes a family of functions differing by a constant.
- Finding antiderivatives is mainly used in evaluating definite integrals.
- Knowing common antiderivatives is helpful, such as \( \int \sin x \, dx = -\cos x + C \), where \( C \) is the constant of integration.