Question

For the line directed from \[P(x_1,y_1,z_1)\] to \[Q(x_2,y_2,z_2)\], which expression is the direction cosine \[m\]?

Options

• \[m=\frac{x_2-x_1}{PQ}\]

• \[m=\frac{y_2-y_1}{PQ}\]

• \[m=\frac{y_2+y_1}{PQ}\]

• \[m=\frac{z_2-z_1}{PQ}\]

Answer 1

The direction cosine \[m\] corresponds to the positive y-axis. It is the y-coordinate difference divided by the distance: \[m=\frac{y_2-y_1}{PQ}\].