For the resultant of two vectors to be maximum,what must be the angle between them? $(^o)$

If $\vec{A} + \vec{B} = \vec{C}$ and $|\vec{A}| = |\vec{B}| = |\vec{C}|$,then the angle between $\vec{A}$ and $\vec{B}$ is ....... $^o$.

Find the angle between $\vec{A} = 3\hat{i} - \hat{j} + 4\hat{k}$ and the $Z$-axis.

If a unit vector is represented by $0.5\hat i + 0.8\hat j + c\hat k$,then the value of $c$ is

$A$ vector has both magnitude and direction. Does it mean that anything that has magnitude and direction is necessarily a vector? The rotation of a body can be specified by the direction of the axis of rotation,and the angle of rotation about the axis. Does that make any rotation a vector?

Which of the following is independent of the choice of coordinate system?