Could you please copy-paste text based code instead of a screenshot and possibly post a minimal (non-)working example?

I see that you \theta_1 is a function of `t`

: you want \theta_1 to be a `symbols`

instead.

I don’t know if you can `lambdify`

using a function as an argument.

```
using SymPy
using PyCall
sp = pyimport("sympy")
@vars t
x = sp.Function("x")(t)
y = sp.Function("y")(t)
z = x^2+y^2
hz = lambdify(z,(x,y))
hz(1,1)
```

What do you expect the result of `hz(1,1)`

to be? If you expect it to evaluate 1^2+1^2, then

```
using SymPy
@vars x y
z = x^2+y^2
hz = lambdify(z,(x,y))
hz(1,1)
```

Note that you do not need to import `sympy`

directly and that `SymFunction`

is also exposed:

```
using SymPy
@vars t
x = SymFunction("x")(t)
y = SymFunction("y")(t)
z = x^2+y^2
```