Properties, Postulates and Theorems
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polygons 3-Dimensional Geometry
Basic Geometry Concepts
Coordinate Geometry
Segment Addition Postulate The Distance Formula
The distance between the points A(x1, y1) and B(x2,y2) is AB = square root of (x2 - x1)2 + (y2-y1)2.
Unique Line Assumption The Midpoint Formula
The midpoint of the segment joining the points A(x1, y1) and B(x2,y2)has the coordinates [(x1 + x2)/2 [(y1 + y2)/2].
  The Slope Formula
The slope m of the line containing the points (x1, y1) and (x2,y2) is m (y2 - y1) / (x2- x1).
  The equation of a line with slope m and y-intercept b is y = mx + b.
  Two nonvertical lines are parallel if and only if their slopes are equal.
  Two nonvertical lines are perpendicular if and only if the product of their slopes is -1.
  An equation of the circles with center (0,0) and radius r is x2 + y2 = r2.
  An equation of the circle with center (h,k) and radius r is (x - h)2 + (y - k)2 = r2.