### 5.20.2 Primitive and definite integral : risch

The risch command takes one mandatory argument and three optional arguments. The first argument is an expression to be integrated. If the variable is not x, then the second argument is the variable. The third and fourth arguments are the limits of integration for when you want a definite integral.
risch returns a primitive (with one or two arguments) or a definite integral (with four arguments).
Input:

risch(x`^`2)

Output:

x`^`3/3

Input:

risch(x`^`2,x,0,1)

Output:

1/3

Input:

risch(t`^`2,t)

Output:

t`^`3/3

Input :

risch(exp(-x`^`2))

Output :

integrate(exp(x`^`2),x)

that is to say that exp(−x2) has no primitive expressed with usual functions.