1. Triangles I
© M. Tallman

2. Equilateral Triangle All three sides are congruent.
60°
4 inches
4 inches
60°
60°
4 inches
All three sides are congruent.
All three angles are also congruent, 60°.
Note: an equilateral triangle will always have three 60° angles, no matter what the size of the triangle.
© M. Tallman

3. Isosceles Triangle 40° 70° 70° Two sides are congruent.
4 inches
4 inches
70°
70°
3 inches
Two sides are congruent.
One side has a different length.
Two angles are congruent.
One angle is different.
© M. Tallman

4. All sides are different lengths. All angles are different.
Scalene Triangle
5.5 inches
3 inches
110°
50°
20°
7 inches
All sides are different lengths.
All angles are different.
© M. Tallman

5. Right Triangle Has one right angle. 90°
Note: It is not possible for a triangle to have more than one right angle.
© M. Tallman

6. All three angles are acute (less than 90°).
Acute Triangle
70°
50°
60°
All three angles are acute (less than 90°).
© M. Tallman

7. One angle is obtuse (greater than 90 °) .
Obtuse Triangle
110°
One angle is obtuse (greater than 90 °) .
Note: It is not possible for a triangle to have more than one obtuse angle.
© M. Tallman

8. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
c units Y° X°
a units Z°
b units
scalene
obtuse
© M. Tallman

9. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
90° Y°
c units
a units X°
b units
right
scalene
© M. Tallman

10. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse. X°
a units
a units X° X°
a units
equilateral
acute
© M. Tallman

11. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse. X°
b units
b units Y° Y°
a units
isosceles
acute
© M. Tallman

12. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse. X°
a units
b units X°
a units
right
isosceles
© M. Tallman

13. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse. Y°
c units
a units Z° X°
b units
scalene
acute
© M. Tallman

14. Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
Classify the Triangle
Equilateral, Isosceles, Scalene, Right, Acute, Obtuse.
a units
a units Y° X° X°
b units
obtuse
isosceles
© M. Tallman