   5.18.1  Antiderivative and definite integral : integrate int Int

integrate (or int) computes a primitive or a definite integral. A difference between the two commands is that if you input quest() just after the evaluation of integrate, the answer is written with the ∫ symbol.

integrate (or int or Int) takes one, two or four arguments.

• with one or two arguments
an expression or an expression and the name of a variable (by default x),
integrate (or int) returns a primitive of the expression with respect to the variable given as second argument.
Input :
integrate(x^2)
Output :
x^3/3
Input :
integrate(t^2,t)
Output :
t^3/3
• with four arguments :
an expression, a name of a variable and the bounds of the definite integral,
integrate (or int) returns the exact value of the definite integral if the computation was successful or an unevaluated integral otherwise.
Input :
integrate(x^2,x,1,2)
Output :
7/3
Input :
integrate(1/(sin(x)+2),x,0,2*pi)
Output after simplification (with the simplify command) :
2*pi*sqrt(3)/3

Int is the inert form of integrate, it prevents evaluation for example to avoid a symbolic computation that might not be successful if you just want a numeric evaluation.
Input :

evalf(Int(exp(x^2),x,0,1))

or :

evalf(int(exp(x^2),x,0,1))

Output :

1.46265174591

Exercise 1
Let

f(x)=
 x x2−1
+ln(
 x+1 x−1
)

Find a primitive of f.
Input :

int(x/(x^2-1)+ln((x+1)/(x-1)))

Output :

x*log((x+1)/(x-1))+log(x^2-1)+1/2*log(2*x^2/2-1)

Or define the function f, input :

f(x):=x/(x^2-1)+ln((x+1)/(x-1))

then input :

int(f(x))

Output of course the same result.
Warning
For Xcas, log is the natural logarithm (like ln), as log10 is 10-basis logarithm

Exercise 2
Compute :

 2 x6+2 · x4+x2
dx

Input :

int(2/(x^6+2*x^4+x^2))

Output :

2*((3*x^2+2)/(-(2*(x^3+x)))+-3/2*atan(x))

Exercise 3
Compute :

 1 sin(x)+sin(2 · x )
dx

Input :

integrate(1/(sin(x)+sin(2*x )))

Output :

(1/-3*log((tan(x/2))^2-3)+1/12*log((tan(x/2))^2))*2   