Angular coefficient of a straight line

The angular coefficient of a straight line, in the equation y=kx+b on the coordinate plane, is numerically equal to the tangent of the angle (which is the smallest rotation from the Ox axis to the Oy axis) between the positive direction of the abscissa axis and this straight line. The angular coefficient is positive when the function graph increases and negative if the function graph decreases. When the line is parallel to the x-axis, then the angular coefficient does not exist, since it turns to infinity.

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