Inclination of a line is a real number as defined below:
(i) If a line is parallel to – axis or coincides with -axis then
(ii) If a line is not parallel to -axis then let it intersect -axis at a point .
Inclination of is given by
(iii) Inclination of or is defined as the inclination of
If is the inclination of a line then .
Parallel lines have same inclination and conversely.
Inclination of perpendicular line differ by .
Inclination is essentially an angle-measure. The only difference is that inclination can be zero, where as angle-measure can not be zero.
Slope (Gradient) of Non-Vertical Line:
The slope of a non-vertical line is given by , where is the inclination of the line.
Inclination , but slope .
Slope of a vertical line is not defined.
Slope of a line is positive, zero or negative according as the inclination of the line is less than , equal to or greater than respectively.
It is obvious that slope of a line is the ration of its rise or fall to its run
A line with positive slope looks like rising where a line with negative slope looks like falling as we move from left to right along the line.