From 9cd983aa414de680166be314b5f9d6c9182f9218 Mon Sep 17 00:00:00 2001
From: Thomas Guillermo Albers Raviola <thomas@thomaslabs.org>
Date: Wed, 29 Jul 2026 17:11:31 +0200
Subject: Fix derivation of mass loss term

---
 04-bbmd-jor.mac | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/04-bbmd-jor.mac b/04-bbmd-jor.mac
index 808ce36..4062a8e 100644
--- a/04-bbmd-jor.mac
+++ b/04-bbmd-jor.mac
@@ -111,7 +111,8 @@ sim_facts : ev([
   diff(Φc[0],θ)=0,
   diff(Φc[0],θ, 2)=0,
   diff(diff(Φc[0],θ),u)=0,
-  diff(diff(Φc[0],u),θ)=0],
+  diff(diff(Φc[0],u),θ)=0,
+  diff(diff(Φc[0],u),θ,2)=0],
   eval,diff);
 
 coeffs : γβ_facts;
@@ -199,10 +200,13 @@ ce_ev_eqs[2][1]; /* TODO: D_u * c = c_u * D ??? */
 /* Supplementary Condition 1 */
 e_sc_eqs[1] : expand_equation(expand(exp(2*β)*sc_eqs[1]), coeffs)$
 /* BUG */
-e_sc_eqs[1] : subst(coeffs, e_sc_eqs[1])$
+e_sc_eqs[1] : subst(sim_facts, e_sc_eqs[1])$
 eq_mono : block(
-  [eq : coeff(e_sc_eqs[1], r, -2)=0],
-  trigreduce(expand(solve(eq, diff(M,u)))));
+  [eq : coeff(e_sc_eqs[1], r, -2)=0, sim_facts:sim_facts],
+  push(subst(sim_facts, expand(diff(Φu_coeffs[2],u))), sim_facts),
+  eq : solve(eq, diff(M,u))[1],
+  eq : subst(sim_facts, eq),
+  trigreduce(expand(trigsimp(eq))));
 
 /* Supplementary Condition 2 */
 e_sc_eqs[2] : block(
-- 
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