NCERT Miscellaneous Exercise Q17 - Vector Algebra
Question: Let a and b be unit vectors and theta the angle between them. Then a+b is a unit vector if (A) theta=pi/4 (B) theta=pi/3 (C) theta=pi/2 (D) theta=2pi/3.
Answer: (D).
Full step-by-step NCERT solution with diagrams on Something by Zero.