# trapezoidal rule

• Dec 18th 2008, 02:35 PM
nystudent2729
trapezoidal rule
I need to approximate the definite integral using the trapezoidal rule of:
integral(lower bound 1)(upper bound 5) 1/x^2 * dx; n=4
• Dec 18th 2008, 03:14 PM
skeeter
Quote:

Originally Posted by nystudent2729
I need to approximate the definite integral using the trapezoidal rule of:
integral(lower bound 1)(upper bound 5) 1/x^2 * dx; n=4

$f(x) = \frac{1}{x^2}
$

$\int_1^5 f(x) \, dx \approx \frac{1}{2}\left[f(1) + 2f(2) + 2f(3) + 2f(4) + f(5)\right]
$
• Dec 18th 2008, 07:38 PM
nystudent2729
Trapezoid error estimate
I need help finding the trapezoid error estimate of: integral(upper bound 5)(lower bound 1) 1/x^2 *dx; n=4
Thanks.(Worried)
I know that the formula is M(b-a)^3/12n^2 but I am having trouble understanding how to find M.
• Dec 19th 2008, 12:08 AM
mr fantastic
Quote:

Originally Posted by nystudent2729
I need help finding the trapezoid error estimate of: integral(upper bound 5)(lower bound 1) 1/x^2 *dx; n=4
Thanks.(Worried)
I know that the formula is M(b-a)^3/12n^2 but I am having trouble understanding how to find M.

I assume that this is an upper bound estimate of the error where M is the maximum value of $f''(x)$ over the interval [1, 5] and $f(x) = \frac{1}{x^2}$ ....