UPSC 2017 CDS I Math Paper

In ΔOAB and ΔOCD
∠OAB = ∠OCD (Pair of alternate angles)
∠OBA = ∠ODC (Pair of alternate angles)
∴ ΔOBA ~ ΔOCD (AA Similarity)
⇒

OB

OD

⇒

OA

OC

=

AB

CD

(Corresponding sides are proportional)
Thus, the ratio of OA to OC is equal to the ratio of OB to OD