证明：∵MN∥PQ，∴∠MAC=∠ACQ、∠ACP=∠NAC，∵AB、CD分别平分∠MAC和∠ACQ，∴∠BAC=12∠MAC、∠DCA=12∠ACQ，又∵∠MAC=∠ACQ，∴∠BAC=∠DCA，∴AB∥CD，∵AD、CB分别平分∠ACP和∠NAC，∴∠BCA=12∠ACP、∠DAC...