Answer
Acute
Work Step by Step
For angles $\theta$ between $0°$ and $90°$, $\cos\theta$ is positive, for $\theta=90°$ we have $\cos\theta=0$ and for $\theta$ between $90°$ and $180°$, $\cos\theta$ is negative.
Therefore,
(i). If the dot product is positive, then the angle between vectors is acute.
(ii). If the dot product is $0$, then the angle between vectors is the right angle.
(iii). If the dot product is negative, then the angle between vectors is obtuse.
Hence, if the dot product of two vectors is a positive number, then the angle between them is $\textbf{acute}$.
