Since x-axis is normal to the circle at O, and normal to the circle passes through its centre. So, OB is a diameter.
Now, perpendicular from centre of circle to chord bisects the chord, so PA=AQ=λ(Let)
Also, product of segments of chords in a circle is equal i.e. OA⋅AB=AP⋅AQ
⇒1⋅12=λ⋅λ
⇒λ=23 units

Now, area of ΔPQB=21×PQ×AB=21×2λ×AB
i.e. Δ=21⋅43×12 sq. units
=243 sq. units
