Review of Analytic Geometry

Direction Cosines of a Line



Plane Geometry: To locate the position of point P in a two-dimensional space, we can use either the rectangular coordinates (x,y) or the polar coordinates (r, θ). The transformation between these two coordinate systems takes the form

equation
equation
(1)
or
equation
(2)

To calculate the distance d between points P1 and P2, we use

equation
equation
(3)

The slope of the line connecting points P1 and P2 is given by

equation
(4)

To describe the straight line that passes through points P1 and P2, we use

equation
(5)

where m is the slope of the line and b is the y intercept, which is found by knowing m and the coordinates of any point on the line. For example, if we were to use the coordinates of point P1, then we have equation

Solid Geometry: To locate the position of point P in a three-dimensional space, we can use either the rectangular coordinates (x,y,z) or the cylindrical coordinates (r,θ,z). The transformation between these two coordinate systems takes the form

figure
equation
(6)
or
equation
(7)

where θ is measured from the x axis.


Direction Cosines of a Line