Slope is a mathematical and geometric term, which is a quantity indicating the inclination of a straight line (or tangent of a curve) relative to a (horizontal) coordinate axis. It is usually expressed by the tangent of the angle between a straight line (or the tangent of a curve) and a (horizontal) coordinate axis, or the ratio of the difference between the ordinate and abscissa of two points. Slope, also known as "angle coefficient", is the tangent of the positive included angle of a straight line relative to the horizontal axis, reflecting the inclination of the straight line relative to the horizontal plane. The tangent value of the angle formed by a straight line and the positive and semi-axis directions of the horizontal coordinate axis of the plane rectangular coordinate system is the slope of the straight line relative to the coordinate system. If the straight line is perpendicular to the X axis, then the tangent of the right angle is tan90, so the straight line has no slope (it can also be said that the slope of the straight line is infinite). When the slope of the straight line L exists, for the linear function y=kx+b (oblique section), k is the slope of the function image.