In Exercises 11–22, estimate the minimum number of subintervals needed to approximate the integrals with an error of magnitude less than 10^-4 by (a) the Trapezoidal Rule (The integrals in Exercises 11–18 are the integrals from Exercises 1–8.)
∫ from 0 to 3 of 1/√(x + 1) dx

Verified step by step guidance

1. Identify the function to be integrated: \(f(x) = \frac{1}{\sqrt{x + 1}}\) over the interval \([0, 3]\).
2. Recall the error bound formula for the Trapezoidal Rule: \(|E_T| \leq \frac{(b - a)^3}{12 n^2} \max_{a \leq x \leq b} |f''(x)|\), where \(n\) is the number of subintervals.
3. Compute the first derivative \(f'(x)\) and then the second derivative \(f''(x)\) of the function \(f(x)\).
4. Find the maximum absolute value of \(f''(x)\) on the interval \([0, 3]\) by analyzing \(f''(x)\) or evaluating it at critical points and endpoints.
5. Set the error bound \(\frac{(3 - 0)^3}{12 n^2} \max |f''(x)| < 10^{-4}\) and solve this inequality for \(n\) to estimate the minimum number of subintervals needed.

Key Concepts

Trapezoidal Rule

The Trapezoidal Rule is a numerical method to approximate definite integrals by dividing the interval into subintervals and approximating the area under the curve as trapezoids. The accuracy depends on the number of subintervals; more subintervals generally yield better approximations.

Error Bound for the Trapezoidal Rule

The error bound for the Trapezoidal Rule estimates the maximum possible error in the approximation. It depends on the second derivative of the integrand and the number of subintervals. Specifically, the error is bounded by (b−a)^3/(12n^2) times the maximum of |f''(x)| on [a,b].

Second Derivative and Its Role in Error Estimation

The second derivative of the function indicates the concavity and affects the error in the Trapezoidal Rule. To estimate the error bound, one must find the maximum absolute value of the second derivative on the interval, which helps determine how many subintervals are needed for a desired accuracy.