Thread: Numerical integration?

Hello everyone

I have to integrate the definite integral square root(x) using the trapezoidal rule

n=8

from x=4 to x=9

I did (9-4)/8

giving me a width of 5/8

then I did

((9-4))/((2n)) giving me 5/16

I did

(4)^(1/2)+2(4.625)^(1/2)+2(5.25)^(1/2)+2(5.875)^(1/2)+ 2(6.5)^(1/2)+(7.125)^(1/2)+2(7.75)^(1/2)+2(8.375)^(1/2)+1(9)^(1/2) times ((5/16))

But what could be wrong?

There could be lots of things wrong, but you have not shown any such incorrect thing. If you managed an incorrect result, the error appears to be in the final arithmetic. What did you get? I get 12.66395614 or so. That's a good approximation to 38/3.

Before I do the times ((5/16)) part I end up getting 40.52 and I checked many times entering the same numbers as above.