A vector a→ is turned without a change in its length through a small angle dθ. The value of |Δa→| and ∆a are respectively

From the figure |OA→|=a and |OB→|=aAlso from triangle rule OB→−OA→=AB→=Δa→⇒ |Δa→|=AB Using,  angle = arc  radius ⇒ AB=a⋅dθ So,  |∆a→|=adθΔa means change in magnitude of vector, i.e., |OB→|−|OA→|⇒ a−a=0 So  Δa=0