[STATEMENT]
lemma approx_trans2: "r \<approx> x \<Longrightarrow> s \<approx> x \<Longrightarrow> r \<approx> s"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. \<lbrakk>r \<approx> x; s \<approx> x\<rbrakk> \<Longrightarrow> r \<approx> s
[PROOF STEP]
by (blast intro: approx_sym approx_trans)