# Inclination of a Line

The inclination of a line is the angle θ which the part of the line (above the x-axis) makes with x-axis.

If measured in anti-clockwise direction then the inclination θ is positive and if measured in clockwise direction then the inclination θ is negative.

The inclination of a line or the angle of inclination of the line is the angle which a straight line makes with the positive direction of x-axis measured in the anti-clockwise direction to the part of the line above the x-axis. The inclination is usually denoted by θ.

Notes:

(i) The inclination of x-axis and every line parallel to x-axis is 0°

i.e. the inclination of a line parallel to x-axis or the x-axis itself is 0°.

(i) The inclination of y-axis and every line parallel to y-axis is 90°

i.e. the inclination of a line parallel to y-axis or the y-axis itself is 90°.