Question

plz solve question number 18,19,20
fast....​

Answer 1

18) see the attachment for the diagram

We need to prove that ∠ AOC = ∠ BOD

and ∠ AOD = ∠ BOC.

Now, ray OA stands on line CD.

Therefore, ∠ AOC + ∠ AOD = 180°

(Linear pair axiom) ………..(1)

Can we write ∠ AOD + ∠ BOD = 180°?

(Linear pair axiom)……………(2)

From (1) and (2), we can write

∠ AOC + ∠ AOD = ∠ AOD + ∠ BOD

This implies that ∠ AOC = ∠ BOD

Similarly, it can be proved that ∠AOD

= ∠BOC

The soln. to no. 19 and 20 are given

in the attachment