/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 53 Evaluate the definite integrals ... [FREE SOLUTION] | 91Ó°ÊÓ

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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 \( \sqrt{2} \approx 1.414 \):\[ 1 - 0.707 \approx 0.293 \].

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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:
  • \( \int_{a}^{b} f(x) \, dx = F(b) - F(a) \)
This means the definite integral of \( f(x) \) from \( a \) to \( b \) is simply the difference between the values of the antiderivative \( F \) evaluated at \( b \) and \( a \). In our exercise, this theorem helps us compute \( \int_{0}^{\pi/4} \sin x \, dx \) by finding its antiderivative, \(-\cos x\), and substituting the upper and lower limits.
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 \( \sqrt{2} \approx 1.414 \).
These techniques provide useful estimations, especially when employing computational tools for complex or non-analytic functions.
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.
Understanding how to integrate and differentiate these functions is crucial in solving real-world problems involving waves, oscillations, and circular motion.
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.
This understanding allows us to apply limits to find exact solutions, like substituting into the antiderivative to calculate the exact integral of a function.

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