Question

The measure of ∠1 =

20
40
80

Answer 1

answer

∠1 = 20 x 2 = 40

answer
40

Answer 2

40

Explanation:

Given is a circle and also a minor arc. The minor arc subtends angle 1 at the centre of the circle.

Another angle 20 degrees is shown which is the angle subtended by the same minor arc at a point on the circumference.

Recollect circle theorem on central angle as

The arc subtends always an angle twice that of the angle subtended by it at any point on the circumference.

Applying the above here we get

angle 1 = 2 times angle 20

i.e. angle 1 = 40 degrees

Option 2 is right.