1
$\begingroup$

I would to make this substitution with 2 rules. Nothing is happening.

     (Sin[η2] ((Cos[θ2]* Cos[ψ1])/Sin[ψ1] + 
       Cos[ψ2] Sin[θ2]) == Cos[η2] Sin[ψ2]) /. 
  Sin[ψ1] -> (Cos[ϕ2] Sin[η2])/Sin[ψ2] /. 
 Cos[ψ1] -> Cos[η2] Cos[θ2] Cos[ϕ2] - 
   Sin[θ2] Sin[ϕ2]

Have you an idea why i didn't manage to make these substitutions ? Sorry if my question is may be very simple, but i blocked.

$\endgroup$
1
$\begingroup$

Use HoldForm to stop Mathematica from simplifying,

SC = HoldForm[(Sin[\[Eta]2] ((Cos[\[Theta]2]*Cos[\[Psi]1])/
        Sin[\[Psi]1] + Cos[\[Psi]2] Sin[\[Theta]2]) == 
    Cos[\[Eta]2] Sin[\[Psi]2])]

SC /. Sin[\[Psi]1] -> (Cos[\[Phi]2] Sin[\[Eta]2])/Sin[\[Psi]2] /. 
 Cos[\[Psi]1] -> 
  Cos[\[Eta]2] Cos[\[Theta]2] Cos[\[Phi]2] - 
   Sin[\[Theta]2] Sin[\[Phi]2]
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.