how to get a number from integration

THIS IS MY CODE AND I GET Dmax as anequation and i need a final answer as a number, how can i get it?

syms x

L=3000/1000;

b=40/1000;

t=4/1000;

h=100/1000;

H=200/1000;

E=70e9;

Ra=11.25e3;

I=((b/12)*(h+x*(H-h)/L)^3)-((b-2*t)/12)*(h-2*t+x*(H-h)/L)^3

M=Ra*x-5*x^2

dM=x

Dmax= int(((M*dM)/(E*I)),1.125,3)

Answer 1

[John D'Errico]

syms x
L=3000/1000;
b=40/1000;
t=4/1000;
h=100/1000;
H=200/1000;
E=70e9;
Ra=11.25e3;
I=((b/12)*(h+x*(H-h)/L)^3)-((b-2*t)/12)*(h-2*t+x*(H-h)/L)^3;
M=Ra*x-5*x^2;
dM=x;
(M*dM)/(E*I)

ans = 

That is the kernel you wish to integrate. I see it is a function only of x, and that is good. However, it is also a bit complicated. The integral you wish to see would possibly be difficult. See what happens when we integrate.

Dmax= int(((M*dM)/(E*I)),1.125,3)

Dmax = 

And MATLAB tells us the solution is the question itself. That is, it was unable to perform the integral, yielding an analytical solution. However, you can perform a numerical integration. Nothing impedes you from that.

Dmax= vpaintegral(((M*dM)/(E*I)),1.125,3)

Dmax = 

0.252672