Find the approximated integral value of an equation 1/(x+1) using Simpson's 1/3 rule
a = 0 and b = 1
Interval n = 5Solution:Equation is `f(x)=(1)/(x+1)`
`a=0`
`b=1`
`Delta x =(b-a)/n=(1 - 0)/5=0.2`
The value of table for `x` and `f(x)`
| `x` | `f(x)` |
| `x_0=0` | `f(x_(0))=f(0)=1` |
| `x_1=0.2` | `f(x_(1))=f(0.2)=0.8333` |
| `x_2=0.4` | `f(x_(2))=f(0.4)=0.7143` |
| `x_3=0.6` | `f(x_(3))=f(0.6)=0.625` |
| `x_4=0.8` | `f(x_(4))=f(0.8)=0.5556` |
| `x_5=1` | `f(x_(5))=f(1)=0.5` |
Method-1:Using Simpsons `1/3` Rule
`int f(x) dx=(Delta x )/3 (f(x_(0))+4(f(x_(1))+f(x_(3))+f(x_(5))+...+f(x_(n-1)))+2(f(x_(2))+f(x_(4))+f(x_(6))+...+f(x_(n-2)))+f(x_(n)))`
`int f(x) dx=(Delta x )/3 [f(x_(0))+4f(x_(1))+2f(x_(2))+4f(x_(3))+2f(x_(4))+f(x_(5))]`
`f(x_(0))=1`
`4f(x_(1))=4*0.8333=3.3333`
`2f(x_(2))=2*0.7143=1.4286`
`4f(x_(3))=4*0.625=2.5`
`2f(x_(4))=2*0.5556=1.1111`
`f(x_(5))=0.5`
`int f(x) dx=0.2/3*(1+3.3333+1.4286+2.5+1.1111+0.5)`
`=0.2/3*(9.873)`
`=0.6582`
Solution by Simpson's `1/3` Rule is `0.6582`
Method-2:Using Simpsons `1/3` Rule
`int f(x) dx=(Delta x )/3 (f(x_(0))+4(f(x_(1))+f(x_(3))+f(x_(5))+...+f(x_(n-1)))+2(f(x_(2))+f(x_(4))+f(x_(6))+...+f(x_(n-2)))+f(x_(n)))`
`int f(x) dx=(Delta x )/3 [(f(x_(0))+f(x_(5)))+4(f(x_(1))+f(x_(3)))+2(f(x_(2))+f(x_(4)))]`
`=0.2/3 [(1 +0.5)+4xx(0.8333+0.625)+2xx(0.7143+0.5556)]`
`=0.2/3 [(1 +0.5)+4xx(1.4583)+2xx(1.2698)]`
`=0.2/3 [(1.5)+(5.8333)+(2.5397)]`
`=0.6582`
Solution by Simpson's `1/3` Rule is `0.6582`
This material is intended as a summary. Use your textbook for detail explanation.
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