# Find this integral

arslan894
f(x) = ∫e^(1-(x^2)/(b^2))dx the limits are -b to b , take the value of b = 3

DivisionByZro
Is this the integral?
$$\int_{-3}^{3}e^\frac{1-x^2}{9}dx$$

We're not going to do it for you. What have you tried?

arslan894
bro i tried it using substitution but the problem is that i cant go much further, @ DivisionByZro exp(1-(x^2/9))^.5

DivisionByZro
Is this it?
$$\int_{-3}^{3}e^\sqrt{1-\frac{x^2}{9}}dx$$

arslan894
yes bro

DivisionByZro
Well, in any case, you won't find any substitutions since you don't have any "x" term multiplying the expression, therefore whatever you have in the exponent part can't be reduced. In other words, it wouldn't be as hard if your integral was something like:

$$\int_{-3}^{3}xe^{x^{2}}dx$$

In this case if you let u=x2, then du=2xdx, and you could use substitution.

arslan894
i was modeling in matlab to find the friction between cam follower of an engine ,i used int function in matlab but it gave warning that explicit answer doesnt exist ,i used the simpson 38 rule to find the solution on paper but dont know how to use simpson 38 rule in matlab.

arslan894
any one knows how to do this function using simpson 3 8 rule in matlab ?

bhartish
I also have a doubt . Anybody reply fast

How to integrate

exp(x)*erfc(x) in MATLAB