triangle

1
triangle a three sided polygon (straight sides
closed)
A
3 sides 3 angles 3 vertices A, B, C
B
C
2
Classify triangles by sides

• isosceles triangle at least two sides are
  congruent

F
legs base
D
E
3
Classify triangles by sides

• scalene triangle no sides are congruent

4
Classify triangles by sides

• equilateral triangle all three sides are
  congruent

5
Classify triangles by angles

• acute triangle all three angles are acute (less
  than 90º)

6
Classify triangles by angles

• right triangle one right angle (exactly 90º)
  two acute angles the acute angles are
  complementary (they add up to 90)

legs hypotenuse
7
Classify triangles by angles

• obtuse triangle one obtuse angle (more than
  90º) two acute angles

8
Classify triangles by angles

• equiangular triangle all three angles are
  congruent (60º)

9
altitude or height - a segment from a vertex
perpendicular to the opposite side may be
inside, outside or on the triangle
10
median middle segment from a vertex to the
midpoint of the opposite side must be inside the
triangle
11
angle bisector segment from a vertex to the
opposite side that bisects the angle