解:设角DBE=a,则角EDB=a,角AED=角DBE+角EDB=2a,角EAD=角AED=2a,角BDC=角ABD+角BAD=3a,角BCD=角BDC=3a,角ABC=角ACB=3a,角A+角C+角B=180°,∴2a+3a+3a=180°a=22.5°所以角A=45°
设∠A=α,则∠AED=∠α,∠EBD=∠α/2,∠C=∠BDC=3/2∠α得∠α+3∠α=180°,∠A=45°主要根据内角和=180°