how to integrate a graph

A function is given for a definite interval. Infact exact problem coding is not required.The solution must be general.

1. f(x)=x^2;0<x<5
2. f(x)=x;5<x<8

Now how to integrate this and plot this I came up with

syms x

c=int(x^2)

then using heaviside function I could plot e.g c.*heaviside(t)-c.*heaviside(t-5);first part

But how do you convert the sym to matlab variable again

Help is higlhy appreciated

Answer 1

[KSSV]

syms x
f = x^2 ;
% integration 
c =  int(f) ;
% plot 
xx = linspace(0,5) ;
plot(xx,double(subs(c,xx)))