the spot is quartzose.
sent1: the fact that the hemstitch either does sail or is not a kind of a sawm or both is incorrect. sent2: if the spot is not quartzose then either the hemstitch sails or it is not a sawm or both.
void -> assump1: Let's assume that the spot is not quartzose.; sent2 & assump1 -> int1: the hemstitch is a sail and/or it is not a sawm.; int1 & sent1 -> int2: this is contradiction.; [assump1] & int2 -> hypothesis;
$hypothesis$ = the spot is quartzose. ; $context$ = sent1: the fact that the hemstitch either does sail or is not a kind of a sawm or both is incorrect. sent2: if the spot is not quartzose then either the hemstitch sails or it is not a sawm or both. ; $proof$ = 
void -> assump1: Let's assume that the spot is not quartzose.; sent2 & assump1 -> int1: the hemstitch is a sail and/or it is not a sawm.; int1 & sent1 -> int2: this is contradiction.; [assump1] & int2 -> hypothesis; __PROVED__