﻿ Triangle defined by 3 points
Triangle Defined by 3 Points
 X1 Y1 X2 Y2 X3 Y3
 Area Perimeter Intersection point (x,y) of the medians: Intersection point (x,y) of the altitudes: Incircle radius: Circumcircle radius:
 intersection point of the angles bisector (incircle center) intersection point of the sides perpendicular bisectors (circumcircle center):
 Side 1 - 2 Side 1 - 3 Side 2 - 3 Angle   α Angle   β Angle   γ Altitude h1 Altitude h2 Altitude h3 Median m1 Median m2 Median m3
 Equations of triangle defined by 3 points ▲
Triangle given by 3 points
(x1 , y1), (x2 , y2) and (x3 , y3)
 The area is given by: Perimeter (P) Triangle angles: We have to remember that if the result of the angle is negative then we have to transelate it into a positive angle by the formula:     angle = 2 · pi   angle.
Intersection point of the medians. Intersection point of the medians (x , y)
(centroid - also knowen as the center of gravity).

The lengths of the medians are:
Intersection point of the triangle altitudes (orthocenter)
After solving the determinants x and y will be:
The lengths of the altitudes are found by the formulas:
Intersection point of the sides perpendicular bisectors (circumcircle)
After solving the determinants we get the x and y coordinates:
The circumcircle radius can be found by calculating the distance of the center point (x , y) from any one of the triangle vertices:
Intersection point (x , y) of the angles bisectors (incircle)
We denote a, b and c as the lengths of the triangle sides.
The incircle radius can be found by calculating the distance of the center point (x , y) from one of the sides of the triangle: