Angle Inclination of a Line
The angle inclination of a line is the angle formed by the intersection of the line and the x-axis. Using a horizontal "run" of 1 and m for slope, the angle of inclination, theta=tan-1(m), or m=tan(theta). Therefore, if the angle or the slope is known, the other can be found using one of the equations. If the angle of inclination is negative, then the slope of the line is also negative.