∵M、N、P分别是AD、BC、BD的中点,AB=CD
∴MP平行等于AB/2,NP平行等于CD/2
∴MP=NP
∴∠PMN=∠PNM=[180°-∠MPN]/2=[180°-(∠MPD+∠NPD)]/2
∵∠MPD=∠ABD=20°
∠NPD=180°-∠BPN=180°-∠BDC=110°
∴∠PMN=25°
∵M、N、P分别是AD、BC、BD的中点,AB=CD
∴MP平行等于AB/2,NP平行等于CD/2
∴MP=NP
∴∠PMN=∠PNM=[180°-∠MPN]/2=[180°-(∠MPD+∠NPD)]/2
∵∠MPD=∠ABD=20°
∠NPD=180°-∠BPN=180°-∠BDC=110°
∴∠PMN=25°