RA and RB are two tangents from a common point ‘R’ outside the circle with centre ‘O’, having a radius of 6 cm. If ∠ARB = 70°, find the measure of the angle AOB

110°

In quadrilateral AOBR

∠A + ∠B + ∠O + ∠R = 360º

[ Angle made by radius on tangent touching circumference is 90º ]

90º + 90º + ∠O + 70º  = 360º 

∠O = 110º 

So, ∠AOB = 110º