ABCD

∴∠ABC=∠BCD=40o

AB = AO

∴∠O=∠ABO=X

∠CAB=2X

CB = AB

∴∠ACB=CAB=2X

∴2X+40+x+x= 180

∴x=35o

∴∠COD=35o

Question 2: Junior high school math problems, geometry problems.

Known in △ABC, ∠CAB=2α, 0