Find the approximated integral value of an equation 1/(x+1) using Trapezoidal 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 Trapezoidal Rule
`int f(x) dx=(Delta x )/2 (f(x_(0))+2(f(x_(1))+f(x_(2))+f(x_(3))+...+f(x_(n-1)))+f(x_(n)))`
`int f(x) dx=(Delta x )/2 [f(x_(0))+2f(x_(1))+2f(x_(2))+2f(x_(3))+2f(x_(4))+f(x_(5))]`
`f(x_(0))=1`
`2f(x_(1))=2*0.8333=1.6667`
`2f(x_(2))=2*0.7143=1.4286`
`2f(x_(3))=2*0.625=1.25`
`2f(x_(4))=2*0.5556=1.1111`
`f(x_(5))=0.5`
`int f(x) dx=0.2/2*(1+1.6667+1.4286+1.25+1.1111+0.5)`
`=0.2/2*(6.9563)`
`=0.6956`
Solution by Trapezoidal Rule is `0.6956`
Method-2:Using Trapezoidal Rule
`int f(x) dx=(Delta x )/2 (f(x_(0))+2(f(x_(1))+f(x_(2))+f(x_(3))+...+f(x_(n-1)))+f(x_(n)))`
`int f(x) dx=(Delta x )/2 [f(x_(0))+f(x_(5))+2(f(x_(1))+f(x_(2))+f(x_(3))+f(x_(4)))]`
`=0.2/2 [1 +0.5 + 2xx(0.8333+0.7143+0.625+0.5556)]`
`=0.2/2 [1 +0.5 + 2xx(2.7282)]`
`=0.2/2 [1 +0.5 + 5.4563]`
`=0.6956`
Solution by Trapezoidal Rule is `0.6956`
This material is intended as a summary. Use your textbook for detail explanation.
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