[STATEMENT]
lemma d_IN_h_source [simp]: "d_IN (h_diff i) (source \<Delta>) = 0"
[PROOF STATE]
proof (prove)
goal (1 subgoal):
 1. d_IN (h_diff i) (source \<Delta>) = 0
[PROOF STEP]
by(simp add: d_IN_def h_diff_def cong del: if_weak_cong)