straight lines - slope of perpendicular straight lines
109483
Straight lines - product of slope of perpendicular lines.
43435
How to calculate average slope in a grid?
80670
'Lines' in the Euler phi graph
131209
Finding point coordinates of a perpendicular
146962
Mathematica slope fields
39906
Equation of the locus of the foot of perpendicular from any focus upon any tangent to the ellipse ${x^2\over a^2}+{y^2\over b^2}=1$
26519
Slope layer with false results in QGIS?
87054
line segments with edges into a curve
143101
Find the slope of a line given a point and an angle
43183
basic geometry angle problem
60350
Vector equation and parametric equation for a line segment
109917
Why is the slope of a line defined as the change in y over the change in $x$?
136581
Slope, in which direction?
60202
Find a plane that passes through a point and is perpendicular to 2 planes
107185
Drawing perpendicular lines at start and end of lines using ArcGIS Desktop?
68090
Can we find incentre of a triangle by using equation of lines?
5836
Determining the general perpendicular normal