= 180-( 180-∠A)/2

=90+∠A/2

Think for yourself.

25( 1). (Similar to 24. )

(2)≈BOD = 180-[ 180-(≈A+≈B)/2]

= 180-[ 180-( 180-∠C)/2]= 90-∠C/2

That is ∠BOD=∠GOC

I really don't know what you are talking about.

20. It is better to use a similar delta. AED and admiral. Admiral and AMB. Compare with each other