Input: integrate(integrate(x + y, y))
Write: `integrate(integrate(x + y, y))`
Output: $$ \int \int (x+y)\ dy\ dx == \frac{1}{2}\ {x}^{2}\ y+\frac{1}{2}\ x\ {y}^{2} $$ Result:$$\frac{1}{2}\ {x}^{2}\ y+\frac{1}{2}\ x\ {y}^{2}$$