Find the approximated integral value of an equation 1/x using Simpson's 3/8 rule
a = 1 and b = 2
Step value (h) = 0.25Solution:Equation is `f(x)=(1)/(x)`
`a=1`
`b=2`
The value of table for `x` and `f(x)`
| `x` | `f(x)` |
| `x_0=1` | `f(x_(0))=f(1)=1` |
| `x_1=1.25` | `f(x_(1))=f(1.25)=0.8` |
| `x_2=1.5` | `f(x_(2))=f(1.5)=0.6667` |
| `x_3=1.75` | `f(x_(3))=f(1.75)=0.5714` |
| `x_4=2` | `f(x_(4))=f(2)=0.5` |
Method-1:Using Simpson's `3/8` Rule
`int f(x) dx=(3Delta x )/8 (f(x_(0))+2(f(x_(3))+f(x_(3))+...+f(x_(n-3)))+3(f(x_(1))+f(x_(2))+f(x_(4))+f(x_(5))+...+f(x_(2))+f(x_(n-1)))+f(x_(n)))`
`int f(x) dx=(3Delta x )/8 [f(x_(0))+3f(x_(1))+3f(x_(2))+2f(x_(3))+f(x_(4))]`
`f(x_(0))=1`
`3f(x_(1))=3*0.8=2.4`
`3f(x_(2))=3*0.6667=2`
`2f(x_(3))=2*0.5714=1.1429`
`f(x_(4))=0.5`
`int f(x) dx=(3xx0.25)/8 *(1+2.4+2+1.1429+0.5)`
`=(3xx0.25)/8 *(7.0429)`
`=0.6603`
Solution by Simpson's `3/8` Rule is `0.6603`
Method-2:Using Simpson's `3/8` Rule
`int f(x) dx=(3Delta x )/8 (f(x_(0))+2(f(x_(3))+f(x_(3))+...+f(x_(n-3)))+3(f(x_(1))+f(x_(2))+f(x_(4))+f(x_(5))+...+f(x_(2))+f(x_(n-1)))+f(x_(n)))`
`int f(x) dx=(3Delta x )/8 [(f(x_(0))+f(x_(4)))+2(f(x_(3)))+3(f(x_(1))+f(x_(2)))]`
`=(3xx0.25)/8 [(1 +0.5)+2xx(0.5714)+3xx(0.8+0.6667)]`
`=(3xx0.25)/8 [(1 +0.5)+2xx(0.5714)+3xx(1.4667)]`
`=(3xx0.25)/8 [(1.5)+(1.1429)+(4.4)]`
`=0.6603`
Solution by Simpson's `3/8` Rule is `0.6603`
This material is intended as a summary. Use your textbook for detail explanation.
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