Question

Direction cosines of Z - axis are -

• A. 0,0,1
• B. 0,1,0
• C. 1,0,0
• D. 0,1,1

Answer 1

The correct option is A 0,0,1

We know that the direction cosines of any line is the cosine of the angles it makes from the positive direction of coordinate axes. Z- axis is perpendicular to both X & Y axes so makes ${90}^{\circ }$ with both the axes. Whereas with Z - axis it makes $0^{\circ }$. So, the direction cosines will be -${\text{cos90}}^{\circ }$, ${\text{cos90}}^{\circ }$, ${\text{cos0}}^{\circ }$.
Or 0,0,1.
Similarly the direction cosines for X - axis are 1,0,0
& the direction cosines for Y - axis are 0,1,0