MATLAB: About getting answers with “SYM” function

sym

Hi guys,

Now I am try to getting start with Matlab.

I get a equation

Px=sym('(L1+L2*cos(A2)+L3*cos(A2+A3))*cos(A1)')

A1 A2 A3 L1 L2 L3 are some variables

How can I put the value to those variables and finally get the value of Px?

Thanks a lot!!

   solve(Px==(L1+L2*cos(A2)+L3*cos(A2+A3))*cos(A1), Py==(L1+L2*cos(A2)+L3*cos(A2+A3))*sin(A1), Pz==(L2*sin(A2)+L3*sin(A2+A3)), A1, A2, A3)