class="kt">Prop</span>) : p <span class="bp">‚àß</span> q <span class="bp">‚Üî</span> q <span class="bp">‚àß</span> p :=</span><span class="alectryon-wsp">
</span></span><span class="alectryon-wsp">  </span><span class="alectryon-sentence"><input class="alectryon-toggle" id="literate-lean3-lean-chk5" style="display: none" type="checkbox"><label class="alectryon-input" for="literate-lean3-lean-chk5">apply iff.intro,</label><small class="alectryon-output"><div><div class="alectryon-goals"><blockqu