The answer to the third question of congruent triangles in Chapter 11 of Volume 22 of mathematics eighth grade of new education press
I don't know how to write symbols. Let's see for myself~
Because CD is perpendicular to AB, be is perpendicular to AC,
So BDO = Coe
Because be, CD goes to point o
So angle DOB = angle EOC
And because ob = OC
So the triangle DOB is equal to the triangle EOC
So od = OE
So OA score angle DAE
So angle 1 = angle 2