Mathematics (Geometry) Kinds of Triangles

1. The World of
Triangles
Conrado P. Macapinlac, Sr. High School
Mr. Carlo Justino J. Luna
www.iamcarloluna.blogspot.com

2. Triangles
A triangle is a 3-sided
polygon. Every triangle
has three sides and
three angles. When
added together, the
three angles equal 180°.

3. Classifications:
According to the interior angles:
1. Acute triangle
2. Right triangle
3. Obtuse triangle
4. Equiangular triangle
According to the number of congruent sides:
1. Scalene triangle
2. Isosceles triangle
3. Equilateral triangle

4. Acute Triangle
• An acute triangle
with three acute
interior angles.

5. Right Triangle
• A right triangle is a
triangle with one
right angle.

6. Obtuse Triangle
• An obtuse triangle is
a triangle with one
obtuse angle.

7. Equiangular
Triangle
• An obtuse triangle is
a triangle which has
three equal angles.

8. Scalene Triangle
• A scalene triangle is
a triangle with three
unequal sides.

9. Isosceles Triangle
• An isosceles triangle
is a triangle with two
congruent sides.

10. Equilateral
Triangle
• An equilateral
triangle is a triangle
with three congruent
sides.

11. The Hypotenuse
The hypotenuse of a right
triangle is the triangle's
longest side, i.e., the side
opposite the right angle.

12. Pythagorean theorem
For a right triangle with
legs a and b and
hypotenuse c, a2
+b2
=c2
.

13. Triangle Quiz
Please complete the
following quiz that
covers the information
that was just presented
to you.

14. Question 1
• If a triangle has
three unequal
sides, it is a
______ triangle.
– A) Scalene
– B) Obtuse
– C) Isosceles
• Answer:
– A) Scalene

15. Question 2
• A triangle which
has three equal
angles is a
______ triangle.
– A) Acute
– B) Equilateral
– C) Equiangular
• Answer:
– C) Equiangular

16. Question 3
• A triangle with (at
least) two equal
sides is a ______
triangle.
– A) Scalene
– B) Isosceles
– C) Congruent
• Answer:
– B) Isosceles

17. Question 4
• Two triangles
that are equal are
called ______
triangles
– A) Acute
– B) Obtuse
– C) Congruent
• Answer:
– C) Congruent

18. Question 5
• A triangle with all
three sides of
equal length is a
______ triangle.
– A) Equilateral
– B) Right
– C) Equiangular
• Answer:
– A) Equilateral

19. Question 6
• A triangle with an
angle of 90° is a
______ triangle.
– A) Acute
– B) Right
– C) Congruent
• Answer:
– B) Right

20. Question 7
• A triangle in
which all three
angles are less
than 90° is a
______ triangle.
– A) Right
– B) Acute
– C) Scalene
• Answer:
– B) Acute

21. Question 8
• A triangle in
which one of the
angles is greater
than 90° is a
______ triangle.
– A) Obtuse
– B) Isosceles
– C) Acute
• Answer:
– A) Obtuse

22. Question 9
• What is the
Hypotenuse of a
right triangle?
– A) The smallest
angle.
– B) The side
opposite the right
angle.
– C) The right
angle.
• Answer:
– B) The side
opposite the right
angle.

23. Question 10
• The Pythagorean
Theorem states
…
– A) πr2
– B) (a+b)2
/2=c
– C) a2
+b2
=c2
• Answer:
– C) a2
+b2
=c2

24. Question 11
• Use the
Pythagorean
Theorem to solve
the following:
– a = 5
– b = 12
– c = ?
• Answer:
– c = 13

25. Triangles
Conrado P. Macapinlac, Sr. High School
Mr. Carlo Justino J. Luna
www.iamcarloluna.blogspot.com