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2D SHAPES and ANGLES
What are 2-Dimensional Shapes?
A 2-dimensional shape is a geometric figure
that has length and width but no thickness
or depth.
It is a shape that is flat. There are 2Dimensional shapes everywhere! Point to
a few of them in the classroom.
Triangles
Triangles are also considered a type of
polygon. It is a three sided shape with
three angles. There are different types of
triangles.
Equilateral Triangles
An equilateral triangle is an Isosceles
triangle that has 3 sides that are all equal
in length. That means that side 1,2 is
equal to side 2,3 which is also equal to
side 3,1.
Isosceles Triangles
Isosceles triangles are triangles that have at
least 2 sides that are equal in length. It
looks different from an equilateral triangle.
With a partner, explain how an equilateral
triangle looks different from an isosceles
triangle.
Scalene Triangles
A scalene triangle is a triangle that does not
have any equal sides.
Acute, Obtuse and Right
Triangles
An acute triangle is a triangle that has 3 angles that measure less than
90 degrees.
An obtuse triangle is a triangle that has one angle that measures
greater than 90 degrees.
A right triangle is a triangle that has one angle that measures exactly 90
degrees. It has one right angle.
Measuring Angles
Angles can be measured using a tool called a protractor. To
measure an angle with a protractor…
1) Place the center of the protractor on the angle's vertex.
2) Rotate the protractor so that the straightedge is placed over one of
the angle's sides.
3) Use the scale that begins with zero. Read where the other side of
the angle crosses this scale.