Direction cosines and direction ratios of a line
Three Dimensional Geometry of Class 12
Direction cosines and direction ratios of a line
The direction cosines of a line are defined as the direction cosines of any vector whose support is the given line.
If A(x1, y1, z1) and B(x2, y2, z2) are two points on the line, then its direction cosines are
or 
The direction ratios of a line are the direction ratio of any vector whose support is the given line. If A(x1, y1, z1) and B(x2, y2, z2) are two points on a line, then its direction ratio are x2 − x1, y2 − y1, z2 − z1.
