The first volume of mathematics answers in the seventh grade of the original classroom, pages 26 and 27.
2.( 1) Yes, triangle ABD, triangle CDB (2) Yes, triangle ADB and triangle AFD, triangle ABF and triangle DBF⑶ (3). It is proved that because angle 1= angle 2 and angle 1 ACE= angle 2 ACE, angle ACB= angle DCE is in triangle ACB and triangle DCE, CA=CD, and angle ACB= angle DCE. ...