# The domain of a function: domain

### 5.17.1 The domain of a function: domain

The domain command finds the domain of a function.

- domain takes one mandatory argument and one optional argument:
  - expr, an expression involving a single variable.
  - Optionally, x, the variable, which by default will be x.
- domain(expr ⟨,x⟩) returns the domain of the function defined by expr.

#### Examples.

- Input:
  domain(ln(x+1))
  Output:

  x>−1

- Input:
  domain(asin(2*t),t)
  Output:

  t≥ −

  1
  2

  ∧ t≤

  1
  2