slope, also known as "angle coefficient", indicates the degree of inclination of a straight line relative to the abscissa axis. the tangent value of the angle between a straight line and the positive half-axis direction of the abscissa axis of a certain plane cartesian coordinate system is the slope of the straight line relative to the coordinate system. if the straight line and the x-axis are perpendicular to each other, the tangent of the right angle is infinite, so the straight line has no slope. when the slope of the straight line l exists, for a linear function y=kx+b, (slope-intercept form) k is the slope of the image of the function.