Question

given.
angle ABC =100 degree
to find angle OAC =?​

Answer 1

Answer is 80

Sum of all side of triangle is 180

ABC is 100

100+80=180

Answer 2

Answer:

10°

Step-by-step explanation:

By angle subtended by same chord theorem,

exterior angle AOC = 2×ABC

= 200°

so angle AOC = 360-200

=160°

As OA and OC are radii of the circle they both are equal

So, angle OAC = angle OCA

( angles opposite to equal sides are equal)

ie, AOC + 2x = 180° (angle sum prop.)

x is OAC or OCA

2x = 180-160

x = 20÷2

x = 10

ie, angle OAC = 10°