From a point P, two tangents PA and PB are drawn to a circle with center O as shown.
If angle AOB = 100∘, then find the value of ∠ APB.
As a tangent is perpendicular to the radius through the point of contact,
∠PAO = ∠PBO = 90∘.
The sum of all angles in a quadrilateral is 360∘.
So, ∠APB = 360∘ – 100∘ - 90∘- 90∘ = 80∘.