Question:medium

By trapezoidal rule, approximate value of \(\int_0^6 \frac{dx}{1+x^2}\)

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For trapezoidal rule, equal spacing simplifies calculations.
Updated On: May 21, 2026
  • 1.3128
  • 1.4108
  • 1.4218
  • None of these
Show Solution

The Correct Option is B

Solution and Explanation

The problem requires us to approximate the integral \(\int_0^6 \frac{dx}{1+x^2}\) using the trapezoidal rule. Let's go through the steps involved in solving this using the method.

Trapezoidal Rule Formula:

The trapezoidal rule for approximate integration is given by:

\(T_n = \frac{b-a}{2n} \left[ f(x_0) + 2 \sum_{i=1}^{n-1} f(x_i) + f(x_n) \right]\)

Here, \(a\) and \(b\) are the limits of integration, \(n\) is the number of subintervals, and \(f(x_i)\) are the function values at each subinterval.

Step 1: Defining the function:

The function to integrate is \(f(x) = \frac{1}{1+x^2}\).

Step 2: Setting up parameters:

Given limits are \(a=0\), \(b=6\). Let's use 6 subintervals (n=6) for simplicity.

Step 3: Calculating the width of each interval:

Width, \(h\), is given by:

\(h = \frac{b-a}{n} = \frac{6-0}{6} = 1\)

Step 4: Compute the function values at each subinterval:

  • \(x_0 = 0, \quad f(x_0) = \frac{1}{1+0^2} = 1\)
  • \(x_1 = 1, \quad f(x_1) = \frac{1}{1+1^2} = \frac{1}{2}\)
  • \(x_2 = 2, \quad f(x_2) = \frac{1}{1+2^2} = \frac{1}{5}\)
  • \(x_3 = 3, \quad f(x_3) = \frac{1}{1+3^2} = \frac{1}{10}\)
  • \(x_4 = 4, \quad f(x_4) = \frac{1}{1+4^2} = \frac{1}{17}\)
  • \(x_5 = 5, \quad f(x_5) = \frac{1}{1+5^2} = \frac{1}{26}\)
  • \(x_6 = 6, \quad f(x_6) = \frac{1}{1+6^2} = \frac{1}{37}\)

Step 5: Applying the trapezoidal rule:

\(T_6 = \frac{1}{2} \left[ 1 + 2 \times \left( \frac{1}{2} + \frac{1}{5} + \frac{1}{10} + \frac{1}{17} + \frac{1}{26} \right) + \frac{1}{37} \right]\)

\(= \frac{1}{2} \left[ 1 + 2 \times \left( 0.5 + 0.2 + 0.1 + 0.0588 + 0.0385 \right) + 0.027 \right]\)

\(= \frac{1}{2} \left[ 1 + 1.796 + 0.027 \right]\)

\(= \frac{1}{2} \times 2.823 = 1.4115\)

The computed approximate value is close to 1.4108, which is one of the given options.

Thus, the correct answer is 1.4108.

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