Chapter 1: Problem 135
Suppose that for each \(i\) such that \(1 \leq i \leq N\) one has \(\quad \int_{i-1}^{i} f(t) d t=i^{2} . \quad\) Show \(\quad\) that \(\int_{0}^{N} f(t) d t=\frac{N(N+1)(2 N+1)}{6}\)
Short Answer
Expert verified
The integral \(\int_{0}^{N} f(t) dt\) equals \(\frac{N(N+1)(2N+1)}{6}\) by summing squares.
Step by step solution
01
Understand the Problem
We are given that, for each segment \([i-1, i]\), the integral of \(f(t)\) is equal to \(i^2\). Our goal is to find the integral from 0 to \(N\) and show that it equals \(\frac{N(N+1)(2N+1)}{6}\).
02
Break Down the Integral
Consider the integral \(\int_{0}^{N} f(t) dt\). This integral can be broken down into a sum of individual integrals over each integer interval: \(\int_{0}^{1} f(t) dt + \int_{1}^{2} f(t) dt + \cdots + \int_{N-1}^{N} f(t) dt\), which corresponds to the sum \(1^2 + 2^2 + \cdots + N^2\).
03
Recognize the Sum of Squares Formula
The sum of squares formula is given by \(1^2 + 2^2 + \cdots + N^2 = \frac{N(N+1)(2N+1)}{6}\). This is a well-known formula for the sum of squares of the first \(N\) natural numbers.
04
Apply the Sum of Squares Formula
Since each integral \(\int_{i-1}^{i} f(t) dt = i^2\), it follows that \(\int_{0}^{N} f(t) dt = 1^2 + 2^2 + \cdots + N^2\). Applying the sum of squares formula gives \(\int_{0}^{N} f(t) dt = \frac{N(N+1)(2N+1)}{6}\).
05
Conclusion
Having applied the sum of squares formula to the sum of integrals over each sub-interval, we conclude that \(\int_{0}^{N} f(t) dt = \frac{N(N+1)(2N+1)}{6}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Integral Calculus
Integral calculus is a fundamental branch of mathematics concerned with finding the accumulation of quantities. At its core, it focuses on calculating integrals, which can be understood as the area under a curve within a specified interval. In the context of this problem, we have the integral of a function, denoted as \(f(t)\), over various intervals from \(i-1\) to \(i\). The cumulative result from \(0\) to \(N\) gives us insight into the behavior of the function over this entire range.
- It involves calculating areas which help in predicting total accumulated values over time or space.
- The practice forms the foundation for understanding further core calculus concepts like derivatives and the Fundamental Theorem of Calculus.
- Integral calculus helps in various applied fields such as physics, engineering, and economics.
Sum of Squares
The sum of squares is a straightforward yet crucial arithmetic formula used across many mathematical disciplines. It sums the squares of consecutive integers, a technique often utilized in sequences and series. For this problem, the sum \(1^2 + 2^2 + \, \ldots \, + N^2\) can be calculated using the formula \(\frac{N(N+1)(2N+1)}{6}\). This formula simplifies computations and solves the integral challenge by providing a neat expression for the sum:
- Each \(i^2\) represents the value of the integral for each segment.
- Summing these values gives the total integral over the entire interval from 0 to \(N\).
- This formula is a foundational element in algebra, frequently used in statistics and data analysis to measure variability.
Definite Integrals
In calculus, definite integrals are a way to find the area under a curve between two specified points. They provide a numerical value representing this accumulated area. Unlike indefinite integrals, which are more about finding a family of functions, definite integrals result in a specific number. Here's how they play into our problem:
- Each interval \([i-1, i]\) yields a definite integral represented as \(i^2\).
- The role of definite integrals here is to express the integral \(\int_0^N f(t) dt\) as a summation of these individual segments.
- Definite integrals help in understanding total quantities, like distance, mass, or probability, depending on the context.
Mathematical Proof
A mathematical proof is a logical argument verifying the truth of a statement. In this exercise, the proof involves logical reasoning to show that the integral from 0 to \(N\) results in a sum of squares expressed by the sum \(\frac{N(N+1)(2N+1)}{6}\). To establish this proof, we need:
- Understanding of the problem setup, where \(\int_{i-1}^i f(t) dt = i^2\).
- Breaking the overall integral into a sum of known segments \(1^2 + 2^2 + ... + N^2\).
- Application of the sum of squares formula to verify and prove the given integral equation.