Download The World Of Triangles

Sec 5.1
The World Of Triangles
Objectives---What we’ll
learn…


Identify triangles by angles (Acute,
Right & Obtuse)
Identify triangles by sides (Scalene,
Isosceles & Equilateral)
Triangles



A triangle is a 3sided polygon.
Every triangle has
three sides and
three angles.
When added
together, the
three angles
equal 180°.
Acute Triangles

A triangle in which
all three angles are
less than 90°.
Obtuse Triangles

An obtuse triangle
is a triangle in
which one of the
angles is greater
than 90°.
Right Triangles

A right triangle is a
triangle with a 90°
angle.
Triangle Classification by Angles
Equilangular
Acute
Obtuse
3 congruent angles
3 acute angles
1 obtuse angle
Right
1 right angle
Scalene Triangles

A triangle with
three unequal
sides.
Isosceles Triangles

An isosceles
triangle is a triangle
with (at least) two
congruent sides
and two congruent
angles.
Isosceles Triangle Theorem

The following
shows that if
two sides of a
triangle are
congruent, then
the angles
opposite those
sides are
congruent.
Equilateral Triangles

An equilateral
triangle is a triangle
with all three sides
of equal length.
Triangle Classification by Sides
Equilateral
Isosceles
Scalene
3 congruent sides
At least 2 congruent sides
No congruent sides
3 congruent angles
At least 2 congruent angles
No congruent angles
Equiangular Triangles

An equiangular
triangle is a triangle
which has three
equal angles.
Congruent Triangles


Congruent triangles
are triangles whose
corresponding
angles and sides
are congruent.
They are exactly
the same size and
shape.
The Hypotenuse

The hypotenuse of
a right triangle is
the triangle's
longest side, i.e.,
the side opposite to
the right angle.
The Pythagorean Theorem

For a right triangle
with legs a and b
and hypotenuse c,
a2+b2=c2.
Triangle Quiz

Please complete the following quiz that
covers the information that was just
presented to you.
Question 1

If a triangle has
three unequal sides
it is a ______
triangle.



A) Scalene
B) Obtuse
C) Isosceles

Answer:

A) Scalene
Question 2

A triangle which
has three equal
angles is a ______
triangle.



A) Acute
B) Equilateral
C) Equiangular

Answer:

C) Equiangular
Question 3

A triangle with (at
least) two equal
sides is a ______
triangle.



A) Scalene
B) Isosceles
C) Congruent

Answer:

B) Isosceles
Question 4

Two triangles that
are equal are
called ______
triangles



A) Acute
B) Obtuse
C) Congruent

Answer:

C) Congruent
Question 5

A triangle with all
three sides of equal
length is a ______
triangle.



A) Equilateral
B) Right
C) Equiangular

Answer:

A) Equilateral
Question 6

A triangle with an
angle of 90° is a
______ triangle.



A) Acute
B) Right
C) Congruent

Answer:

B) Right
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
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
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.
Question 10

The Pythagorean
Theorem states …



A) pr2
B) (a+b)2/2=c
C) a2+b2=c2

Answer:

C) a2+b2=c2
Question 11

Use the
Pythagorean
Theorem to solve
the following:



a= 5
b = 12
c=?

Answer:

c = 13
This powerpoint was kindly donated to
www.worldofteaching.com
http://www.worldofteaching.com is home to over a
thousand powerpoints submitted by teachers. This is a
completely free site and requires no registration. Please
visit and I hope it will help in your teaching.