Answer: 3
Step-by-step explanation:
The 3D vector consists of 3 axes, let's say x, y and z.
Now, a vector P lies in all of them.
So, the angle it makes with x axis is α
The angle it makes with y axis is β
The angle it makes with z axis is γ
So, to determine the Cartesian components or to resolve the vector into it's Cartesian components we need 3 angles with each axis.