Can a vector have zero component along a line and still have non-zero magnitude?
True
So we have to make
|→A| Cosθ = 0
Where |→A| cannot be 0
So cosθ has to be 0
⇒θ=90∘
So when vector →A is perpendicular to the other →B, the projection of one over the other is zero even if |→A| is non-zero.