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ECIV 301
Programming & Graphics
Numerical Methods for Engineers
Lecture 30
Numerical Integration
& Differentiation
In SummaryNewton-Cotes Formulas
Replace a complicated function or tabulated data with an approximating
function that is easy to integrate
b
a
n
b
a
dxxfdxxfI
nn
nnon xaxaxaaxf
111
Trapezoidal Rule Multiple Application
n
xfxfxfabI
n
n
ii
2
22
10
x a=xo x1 x2 … xn-1 b=xn
f(x) f(x0) f(x1) f(x2) f(xn-1) f(xn)
General Case
2211
1
1
xfwxfwdx)x(fI
Gauss Method calculates pairs of wi, xi for the Integration limits
-1,1
For Other Integration LimitsUse Transformation
Gauss Quadrature
Points
Weighting Factors wi
Function Arguments
Error
2 W0=1.0 X0=-0.577350269 F(4)()
W1=1.0 X1= 0.577350269
3 W0=0.5555556 X0=-0.77459669 F(6)()
W1=0.8888888 X1=0.0
W2=0.5555556 X2=0.77459669
Gaussian Points
Points
Weighting Factors wi
Function Arguments
Error
4 W0=0.3478548 X0=-0.861136312 F(8)()
W1=0.6521452 X1=-339981044
W2=0.6521452 X2=- 339981044
W3=0.3478548 X3=0.861136312