PA and PB are tangents to the circle with centre O such that ∠APB = 50°, Write the measure of ∠OAB.

Soln-

We know that sum of angle of quadrilateral is 360 degree

So,  ∠AOB+∠APB+90°+90°=360°

∠AOB+50°+90°+90°=360°

∠AOB=360°-230°

∠AOB=130° 

now in, 🔺OAB 

∠OAB+∠OBA+∠AOB=180°(∠OAB=∠OBA=90°) 

2∠OAB+130°=180°

2∠OAB=180°-130°

2∠OAB=50°

∠OAB=25° ans...