let L be non empty join-commutative join-associative Huntington ComplLLattStr ; :: thesis: for a, b being Element of L holds a *' (a + b) = a
let a, b be Element of L; :: thesis: a *' (a + b) = a
thus a *' (a + b) = ((a `) + ((((a `) *' (b `)) `) `)) ` by Th18
.= ((a `) + ((a `) *' (b `))) ` by Th3
.= (a `) ` by Th21
.= a by Th3 ; :: thesis: verum