What is the Trapezoidal Rule?

The trapezoidal rule is a rule which is used to find the value of the definite integral of the form ba f(x) dx. We know that the value of the definite integral ba f(x) dx is the area enclosed under the curve y = f(x) and the x-axis in the interval a and b on the x-axis. We calculate this area by dividing the complete area into several small rectangles and then finding their sum. 

In the Trapezoidal rule as the name suggest the area under the curve is divided into several trapezoids and then their sum is found to get the area of the curve. The trapezoidal rule does not provide the best approximation of the area under the curve than the Simpson’s Rule but still, its result is precise enough and this rule is a widely used rule in calculus.

Trapezoidal Rule

The trapezoidal rule is one of the fundamental rules of integration which is used to define the basic definition of integration. It is a widely used rule and the Trapezoidal rule is named so because it gives the area under the curve by dividing the curve into small trapezoids instead of rectangles.

Generally, we find the area under the curve by dividing the area into smaller rectangles and then finding the sum of all the rectangles, but in the trapezoidal rule the area under the curve is divided into trapezoids, and then their sum is calculated. The trapezoidal rule is used to find the value of the definite integrals in numerical analysis. This rule is also called the trapezoid rule or the trapezium rule. Let us learn more about the trapezoidal rule, its formula and proof, example, and others in detail in this article.

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What is the Trapezoidal Rule?

The trapezoidal rule is a rule which is used to find the value of the definite integral of the form b∫a f(x) dx. We know that the value of the definite integral b∫a f(x) dx is the area enclosed under the curve y = f(x) and the x-axis in the interval a and b on the x-axis. We calculate this area by dividing the complete area into several small rectangles and then finding their sum....

Trapezoidal Rule Formula

The trapezoidal rule formula is the formula that is used to find the area under the curve. Now to find the area under the curve using the Trapezoidal Rule,...

Derivation of Trapezoidal Rule Formula

The Trapezoidal Rule formula for calculating the area under the curve is derived by dividing the area under the curve into several trapezoids and then finding their sum....

How to Apply Trapezoidal Rule?

The trapezoidal rule finds the area under the curve by dividing the area under the curve into various trapezoids and then find the sum of all the trapezoids. The trapezoidal rule is not the perfect approximation of the value of the definite integral as it uses the quadratic approximation....

Summation Notation of Trapezoidal Rule

We know that the area of a trapezoid is basically the average of the lengths of the parallel sides multiplied by the height. So, in this case, consider a trapezoid for the ith interval,...

Riemann Sums

The Riemann sums up work on the idea of diving the area under the curve into different rectangular parts. As the number of rectangles increases, the area becomes closer and closer to the current area. In the figure shown below, there is a function f(x). The area under this function is divided into many rectangles. The total area under the curve is the sum of the areas of all the rectangles....

Middle Point Sums

In the Riemann sums, either the left end or the right end of the rectangle touches the curve. In this case, the middle point of the rectangle touches the curve. Everything else is the same as Riemann sums. The figure below shows the function f(x) and different rectangles in the middle point sums....

Solved Example on Trapezoidal Rule

Example 1: Find the area enclosed by the function f(x) between x = 0 to x = 4 with 4 intervals....

Applications of Trapezoid Rule

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