# Solving this differential equation

I'm trying to solve this de but get an error which I don't understand.

```
x = var('x')
y = function('y')(x)
de = diff(y, x) == tan(y) * (y^3 - y)
desolve(de, y)
TypeError: ECL says: changevar: fourth argument must be an atom; found: 'y(_SAGE_VAR_x)
```

I would also like to plot a maximum solution \phi(0) = 0.5.

Thank you