Sum of direction angles of vector [0,1,0] is?

Question

pi/2, 0, pi or 3pi/2? Also explain plz thank you. 

Answer 1

The direction angles are the angles between the vector and the coordinate axis.

 

[0,1,0] points along the y-axis, making a right angle between the x and z axes. So the sum of the angles is pi/2+0+pi/2 = pi (the angle between the y axis is zero).