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Homework Statement
[tex] \int^{ \pi}_{0} sin(x)dx \;\;\;\;\;\;\;\; dx=\frac{ \pi}{2}[/tex]
Homework Equations
Trapezoidal Approximation:
[tex]|f''(x)| \leq M \;\;\;\;\; for \;\;\;\;\; a \leq x \leq b [/tex]
[tex] \frac {b-a}{12}(M)(dx)^{2} = Error [/tex]
Simpson's Rule:
[tex] |f^{(4)}(x)| \leq M \;\;\;\;\; for \;\;\;\;\; a \leq x \leq b [/tex]
[tex] \frac{b-a}{180}(M)(dx)^{4} = Error [/tex]
The Attempt at a Solution
Ok so I have found the correct estimations using both methods easily, the trapezoidal approximation is: 1.5708 and Simpson's Rule is: 2.0944, those numbers check out in the back of the book, but when it comes to finding the error I think that it should be 0 because the max (M) is zero for both the second and fourth derivative but the book says otherwise. Heres what I did:
[tex] y=sin(x) [/tex]
[tex] y'=cos(x) [/tex]
[tex] y''=-sin(x) [/tex]
[tex] y^{(3)}= -cos(x) [/tex]
[tex] y^{(4)}= sin(x) [/tex]
and Trapezoidal Rule using y'' is:
[tex]|y''( \pi)|=0 [/tex]
and
[tex] |y''(0)|=0 [/tex]
and that follows the same for [tex] y^{(4)} [/tex] so M is 0 and thus the entire equation is 0 and Error = 0 but the book states that the error for the trapezoidal approximation is:
[tex] \frac { \pi^{3}}{48} \;\;\;\;\; or \;\;\;\; .65 [/tex]
and the Error for Simpson's Rule is:
[tex] \frac { \pi^{5}}{2880} \;\;\;\; or \;\;\;\; .1 [/tex]
I don't see how they got this... but I don't think the actual error rate is zero either because if it were then the trapezoidal and simpson approximation would be exactly equal, so where did I go wrong?