Download Understanding Triangles Ms. Gilma Escobar Grade 7

Understanding Triangles
Ms. Gilma Escobar Grade 7
Learn the names
of triangles with
equal angles and
or sides.
Learn how to
identify a triangle
by the angle
measurement
inside the triangle.
Learn how to identify
the triangles with two
names.
Triangles classified by their sides:
Equilateral, Isosceles, and Scalene
An equilateral triangle has
three equal sides and three
equal angles, which will
always be 60°. An easy way
to remember this triangle
is to look at the root word
‘equ’ that is the same as
‘equal’.
A scalene triangle does not
have any equal sides or equal
Isosceles triangles always
angles. If you want a trick to
have two equal sides in
remember this triangle,
length, and two equal angles. remember scalene has the
One way to remember is to
letter ‘n’ in it to help you
look at the name, isosceles,
remember there are no equal
and remember that their
sides and or angles.
should be an isolated angle
with a different
measurement.
Triangles classified by their angles:
Acute, Right, and Obtuse
An acute triangle, like
the one in the picture
above, is a triangle with
all three angles less than
(<) 90°. I remember this
triangle by thinking to
myself about how cute
and little the angles are
since they are all less
than 90°.
A right triangle is a
triangle with an angle
of exactly 90°. A 90°
angle is called a right
angle, and that is how
we can remember that
this is a right triangle,
as well as the little
square inside the
triangle that tells us
this is a right angled
triangle.
An obtuse triangle has an
angle that is greater than (>)
90°. As soon as we identify
an angle greater than 90°,
we know that it is an obtuse
triangle. The ‘o’ in obtuse
reminds me of the wider,
rounder angle in this
triangle.
Combining the Names
The triangle above has a
right angle (90°) and also
has two equal angles,
therefore we can name
this a right isosceles
triangle. Can you guess
the measurement of the
other two angles?
This triangle has only
acute angles and no
equal sides, so we can
call it an acute scalene
triangle.
Note: an angle cannot be obtuse and equilateral at the same time.
An equilateral triangle cannot have an obtuse angle because all 3
angles in an equilateral triangle measure 60 degrees.
If a triangle has two
equal sides and one
obtuse angle, we can
call that triangle obtuse
isosceles triangle.
Works Cited
Slide 1 images from:
http://commons.wikimedia.org/wiki/File:Trianglescalene.svg
http://en.wikipedia.org/wiki/Right_triangle
Slide 2 and slide 3 images from:
http://www.mathsisfun.com/triangle.html
Slide four images from:
http://mathworld.wolfram.com/Triangle.html
http://www.basic-mathematics.com/types-of-triangles.html