For the given figure length of OA is : 1.√5 2.√3 3.√5 or √3 4. neither √5 nor √3

By pythagoras theorem, Hypotenuse 2 = Perpendicular 2 + Base 2 ⇒ OA 2 = AB 2 + OB 2 ⇒ OA 2 = 2 2 + 1 2 ⇒ OA 2 = 4 + 1 ⇒ OA = 5 ⇒ OA = . Hence, Option 1 is the correct option.