UPSC CDS 2 2020 Math Paper

We know that the radius from the center of the circle to the point of tangency is perpendicular to the tangent line. Hence, ∠AMO=90°
Also, ∠ANO=90°
It is also given that ∠MAN=70°
Now in quadrilateral AMON,
⇒∠AMO+∠MON+∠ONA +∠NAM=360°
⇒90°+∠MON+90°+70°=360°
⇒∠MON=110°