Question

in fig. angle ACB equal to 40 degree then find angle OAB​

Answer 1

Answer:

angle AOB will be 80°{Angle on centre is double to its circumference}

In triangle AOB

AOB+OAB+OBA=180

BUT OAB=OBA{ MADE BY RADIUS}

2OAB=100

OAB=50°

Answer 2

Angle ACB = 80° ( angle at the circumference is twice angle at the centre )

Triangle AOB is an isoceles triangle ( OA and OB are radii of the circle )

Sum of all angles in a triangle is 180°, and in an Isoceles triangle the base angles are equal

If one angle (AOB) is 80°, then sum of other two angles is 100° ( 180-80=100)

thus, Angle OAB=Angle OBA= 50°