Numerical Differentiation 1 Numerical Differentiation First Order Derivatives The numerical differentiation formula, (5.9), then becomes f0(x k) = xn j=0 f(x j)l0 j (x k) 1 (n 1)! f(n 1)(ξ x k) y j=0 j6= k (x k −x j). (5.10) we refer to the formula (5.10) as a differentiation by interpolation algorithm. example 5.1 we demonstrate how to use the differentiation by integration formula (5.10) in the case where n = 1. Example 2.2.1.1. the velocity of a rocket is given by. v(t) = 2000ln[14 × 104 14 × 104 − 2100t] − 9.8t, 0 ≤ t ≤ 30. where v is given in m s and t is given in seconds. at t = 16 s, a) use the forward difference approximation of the first derivative of v(t) to calculate the acceleration. use a step size of h = 2 s.
Numerical Differentiation 1 Numerical Differentiation First Order Derivatives Example 4.4.1 use forward difference formula with ℎ= 0.1 to approximate the derivative of 𝑟𝑟 (𝑥𝑥) = ln(𝑥𝑥) at 𝑥𝑥 0 = 1.8. determine the. 178. chapter 9: numerical differentiation. numerical differentiation formulation of equations for physical problems often involve derivatives (rate of change quantities, such as v elocity and acceleration). numerical solution of such problems involves numerical evaluation of the derivatives. one method for numerically evaluating derivatives is. H this immediately suggests the approximation. (1) df ≈ Δ f f ( x h)− f ( x) = (2) dx Δx h where the step size h is small but not zero. this is called a finite difference. specifically it's a forward difference because we compare the function value at x with its value at a point “forward” of this along the x axis, x h . • 1 option – curve fit the data and take the derivative of the curve. • fit a 2nd order lagrange interpolating polynomial to each set of 3 adjacent data points: • does not require equally spaced data • differentiate the lagrange interpolating polynomial ()xi−1,xi,xi 1 fit a 2nd order lagrange interpolating polynomial xi 1 xi x x i 1 x y.
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