How to display a symbolic variable as a number?

I am trying to assign a value to a symbolic variable but it is not working.

Here is an example:

syms l0 phi0(t)
r0=0.5*l0*sin(phi0(t))

When use subs nothing changes

subs(r0,l0,2)
ans = 0.5*l0*sin(phi0(t))

when I want it to show

ans=sin(phi0(t))

This causes problems later on in my code when I am trying to solve a system of equations and it thinks that l0 is still a variable.

[Star Strider]

I cannot reproduce that behaviour.

I get exactly the result you want when I run your code in R2016a.

[Walter Roberson]

I would suggest renaming from l0 to L0 because l0 looks too much like 10 and you might be overlooking a place you think is l0 but is really 10