AP EAMCET Engineering 23 Sep 2020 Shift 1 Paper

(a) Let angle between two lines S1 and S2 be θ, then angle between S1 and reflection of S2 with respect to S1 is θ and similarly the angle between S2 and reflection of s1 with respect to S2 is θ, so angle between reflections is 3θ. Since, reflection coincides to each other, so
3θ=π⇒θ=‌

π

3