What is the slope of the line joining the points (x1,y1) and (x2,y2)?
If θ is the angle which the straight line joining the points (x1,y1) and (x2,y2) subtends at the origin, prove that tan θ=x2y1−x1y2x1x2+y1y2 and cos θ=x1x2+y1y2√x21+x21√x22+y22
The slope of a line joining the points (x1,y1) and (x2,y2) is y1−y2x1−x2.
Midpoint of the line joining the points (x1,y1) and (x2,y2) is (x1+x22,y1+y22).