Analytic Geometry - Mathematics for Computer Graphics - page 146

b

a

b

a

c

c

Fig. 10.6. The three medians of a triangle intersect as its centre of gravity.

l

l

h

a a

c
2

c
2

Fig. 10.7. An isosceles triangle has two equal sides l and equal base angles α .

10.1.7 Equilateral Triangle

An equilateral triangle has three equal sides of length l and equal angles of
60 ◦ . The triangle's altitude and area are
h = √ 3
2

A = √ 3
4

l 2

l (10.9)

10.1.8 Right Triangle

Figure 10.8 shows a right triangle with its obligatory right angle. The triangle's
altitude and area are

h = ab
c

A = 1

2 ab

(10.10)