Changes

--><p>{{#ev:youtube|moh07B8dv2k|||||start=480&end=527}}</p>

#<math>(\varphi \land \psi) \land \delta \vdash \varphi \land (\psi \land \delta)</math><!--

#<math>\alpha \vdash \alpha \land \alpha</math>

#<math>\alpha \land \beta, \gamma \land \delta \vdash \gamma \land \beta</math>