Look at Fig. 2.34. Mark a point
(a) A which is in the interior of both ∠1 and ∠2.
(b) B which is in the interior of only ∠1.
(c) Point C in the interior of ∠1.
Now, state whether points B and C lie in the interior of ∠2 also.
Yes, points 6 and C lie in the interior of ∠ 2 also. Since, ∠ 1 is in interior of ∠ 2, then all the points lying inside the ∠ 1, will also lie inside the ∠ 2.