Getting Error while using lambdify

General Usage
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1

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2

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

3

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.

4 
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)
5

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