Download Classifying Triangles

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U n t er r i ch t spl a n
Cl as s if y ing Triang l e s
Altersgruppe: Y e ar 6, Y e ar s 7 & 8
Maths Standards: 6.GM .3 , 7 .GM .4
Online-Ressourcen: P o l yGo l f
Opening
T eacher
present s
St udent s
play
Act ivit y
8
10
10
14
5
min
min
min
min
min
Closing
ZIE L E :
E x pe r i e nc e classification
P r ac t i c e identifying triangles
L e ar n that triangles can be identified by sides or angles
De v e l o p geometry skills
Ope ni ng | 8 min
To each pair of students, hand out the following nine shapes. Ask
the students to place the shapes into three categories.
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Once the students have sorted the shapes, discuss.
A sk: What are the titles of your categories?
Some students may have categorized by color: blue, purple, and
orange.
A sk: Does anyone have different categories?
Some students may have categorized by shape: circle,
rectangle, and triangle.
S ay: We can categorize these shapes in two separate ways: by
color or by shape. Today, we are going to the do the same thing
with triangles. We can categorize them by side length or by angle
measure.
Write on the board:
Triangles by Sides
E q u ila t e r a l – a triangle with all equal sides
I s o s c e le s – a triangle with two equal sides
S c a le n e – a triangle with no equal sides
Triangles by Angles
A c u t e – a triangle with three acute angles
R ig h t – a triangle with one right angle
Ob t u s e – a triangle with one obtuse angle
S ay: If we are categorizing by shape,
belongs in the circle
category. If we are categorizing by color,
belongs in the orange
category. Likewise, we can classify a single triangle in two ways: by
its side length or by its angle measure.
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T e ac he r pr e se nt s P o l yGo l f – C l assi f yi ng T r i angl e s | 10
min
Present Matific ’s episode P o l yGo l f – C l assi f yi ng T r i angl e s
to the class, using the projector.
The goal of the episode is to classify triangles.
E x a m p le :
S ay: Please read the instruction.
Students can read the instruction from the bottom of the screen.
A sk: Are we considering the triangle’s angles or the triangle’s side
lengths?
Students can answer based on the instruction.
A sk: On which triangle should I click?
Click on the triangle that the students indicate.
If this triangle is correct, stars will appear, and the episode will direct
you to click on a new triangle.
If this triangle is incorrect, a small “X” will appear, the instructions will
wiggle, and a new triangle will fall from the top of the screen.
Continue to ask the students which triangle to click on as the
episode proceeds. Once the ball has rolled into the hole, the
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episode will present two more games of golf.
S t ude nt s pl ay P o l yGo l f – C l assi f yi ng T r i angl e s | 10 min
Have the students play P o l yGo l f – C l assi f yi ng T r i angl e s on
their personal devices. Circulate, answering questions as necessary.
A c t i v i t y | 14 min
Distribute paper to the students. Give them the following
instructions.
1. Use the paper in the landscape position.
2. Title the right third of the paper “Polygons Used”.
3. Title the rest of the paper “Polygon Land”.
4. Under the “Polygons Used” title, make the following table.
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5. Create a drawing underneath “Polygon Land”, using only straight lines
and polygons. Be sure to include at least one rectangle, two right
triangles, one acute triangle, and one obtuse triangle. Your drawing can
be realistic or abstract.
6. In the table, record the number of each polygon you used in your
drawing. You can add categories (square, trapezoid, etc.), if you wish.
7. Color your drawing.
Circulate, checking students work.
Collect work when the students are done, to display later.
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C l o si ng | 5 min
A sk: True or False? An acute triangle may also be a right triangle.
False. An acute triangle does not have any right angles. A right
triangle has one right angle.
A sk: True or False? An obtuse triangle has only one obtuse angle.
True. An obtuse triangle has exactly one obtuse angle.
A sk: True or False? An acute triangle may also be an isosceles
triangle.
True. It is possible for an acute triangle to have two equal sides.
A sk: True or False? A right triangle may have more than one right
angle.
False. A right triangle has exactly one right angle.
A sk: True or False? An acute triangle has only one acute angle.
False. An acute triangle has three acute angles.
A sk: True or False? An obtuse triangle may also be an isosceles
triangle.
True. It is possible for an obtuse triangle to have two equal sides.
A sk: True or False? An obtuse triangle may also be a scalene
triangle.
True. It is possible for an obtuse triangle to have three different
side lengths.
A sk: True or False? An obtuse triangle has two acute angles.
True. An obtuse triangle has one obtuse and two acute angles.
A sk: True or False? An isosceles triangle may also be an
equilateral triangle.
True. If a triangle has two equal sides, the third may also be equal
to them.
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