inner angle

The total is 180, ∠ C = 70, ∠ ADE+∠ B = 1 10.

De: ∠a=∠ade

So ae=ed, and the triangle aed is

isosceles triangle

And because point f is the midpoint of ad.

So ef divides ad vertically in two.

I hope I can help you. If you don't understand, ask again.