Write direction cosines of a line parallel to z-axis.
Given
The line is parallel to z- axis.
So the line would be perpendicular to both x-axis and y-axis.
Hence, the angles formed by the line with x-axis & y-axis are 90° and 90° respectively.
Also the angle formed by the line with z-axis is 0°.
The direction cosines of a line are given by, cos α , cos β , cos γ. Where α,β and γ are angles formed by the line with the x,y and z axes respectively.
Here
α = 90°,β = 90° and γ = 0°
α = cos 90°= 0
β = cos 90°= 0
γ = cos 0° = 1
Therefore the direction cosines of the line parallel to z-axis are (0,0,1).