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In calculus, the trapezoidal rule (also known as the trapezoid rule or trapezium rule) [a] is a technique for numerical integration, i.e., approximating the definite integral: (). The trapezoidal rule works by approximating the region under the graph of the function f ( x ) {\displaystyle f(x)} as a trapezoid and calculating its area.
Suppose that we want to solve the differential equation ′ = (,). The trapezoidal rule is given by the formula + = + ((,) + (+, +)), where = + is the step size. [1]This is an implicit method: the value + appears on both sides of the equation, and to actually calculate it, we have to solve an equation which will usually be nonlinear.
After trapezoid rule estimates are obtained, Richardson extrapolation is applied. For the first iteration the two piece and one piece estimates are used in the formula 4 × (more accurate) − (less accurate) / 3 . The same formula is then used to compare the four piece and the two piece estimate, and likewise for the higher estimates
Example: Euler method with the trapezoidal rule [ edit ] A simple predictor–corrector method (known as Heun's method ) can be constructed from the Euler method (an explicit method) and the trapezoidal rule (an implicit method).
A (1, 1) = Trapezoidal (f, tStart, tEnd, h, y0) % Each row of the matrix requires one call to Trapezoidal % This loops starts by filling the second row of the matrix, % since the first row was computed above for i = 1: maxRows-1 % Starting at i = 1, iterate at most maxRows - 1 times % Halve the previous value of h since this is the start of a ...
Another example for an implicit Runge–Kutta method is the trapezoidal rule. Its Butcher tableau is: The trapezoidal rule is a collocation method (as discussed in that article). All collocation methods are implicit Runge–Kutta methods, but not all implicit Runge–Kutta methods are collocation methods.
While not derived as a Riemann sum, taking the average of the left and right Riemann sums is the trapezoidal rule and gives a trapezoidal sum. It is one of the simplest of a very general way of approximating integrals using weighted averages. This is followed in complexity by Simpson's rule and Newton–Cotes formulas.
Shoelace scheme for determining the area of a polygon with point coordinates (,),..., (,). The shoelace formula, also known as Gauss's area formula and the surveyor's formula, [1] is a mathematical algorithm to determine the area of a simple polygon whose vertices are described by their Cartesian coordinates in the plane. [2]