Download Identifying Triangles

1
U n t er r i ch t spl a n
Id e nt if y ing Triang l e s
Altersgruppe:
English Translation of the Japanese Mathematics
Curriculum: 4 .GF .1.a
Online-Ressourcen: Do n' t P o ke A r o und
Opening
T eacher
present s
St udent s
play
Ext ension
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 Do n’ t P o ke A r o und – I de nt i f yi ng
T r i angl e s | 10 min
Present Matific ’s episode Do n’ t P o ke A r o und – I de nt i f yi ng
T r i angl e s to the class, using the projector.
The goal of the episode is to classify triangles by their angles.
E x a m p le :
S ay: Please read the instruction. On which triangles should we tap?
Students should read the instruction at the bottom of the screen.
A sk: How do we identify that type of triangle?
Students should describe its characteristics.
A sk: Which triangles should we click on?
Click on all the triangles that the students identify.
If you click on a triangle that is incorrect, a small “X” will appear, and a
new triangle will fall from the top of the screen.
When you have clicked on all of the triangles that the students have
identified, click on
.
If you have identified all of the qualifying triangles, the episode will
proceed to a new situation.
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If you have not identified all of the qualifying triangles, the instructions
will wiggle.
The episode will present a total of five situations.
S t ude nt s pl ay Do n’ t P o ke A r o und – I de nt i f yi ng T r i angl e s |
10 min
Have the students play Do n’ t P o ke A r o und – I de nt i f yi ng
T r i angl e s on their personal devices. Circulate, answering
questions as necessary.
E x t e nsi o n | 14 min
Have the students work in groups of four. Distribute graph paper
and rulers to each group.
Ask the students to complete the following assignment.
Draw polygons to help you determine the maximum number of right
angles that can exist in a:
1.
2.
3.
4.
triangle
quadrilateral
pentagon
hexagon
When the students have completed the assignment, discuss.
A sk: How many right angles can there be in a triangle?
The maximum number of right angles in a triangle is one. A right
triangle has one right angle and two acute angles.
A sk a student to come to the board to present a drawing of a
triangle with exactly one right angle.
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A possible response:
A sk: How many right angles can there be in a quadrilateral?
The maximum number of right angles in a quadrilateral is four. A
quadrilateral with four right angles is a rectangle.
A sk a student to come to the board to present a drawing of a
quadrilateral with four right angles.
A possible response:
A sk: How many right angles can there be in a pentagon?
The maximum number of right angles in a pentagon is three.
Ask a student to come to the board to present a drawing of a
pentagon with three right angles.
A possible response:
A sk: How many right angles can there be in a hexagon?
The maximum number of right angles in a c o nv e x hexagon is
three. The maximum number of right angles in a c o nc av e
hexagon is five.
A sk a student to come to the board to present drawings of
hexagons.
A possible response for a convex hexagon:
A possible response for a concave hexagon:
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C l o si ng | 5 min
Distribute a small piece of paper. Have students draw triangles, based on the
following specifications.
1. Draw one triangle that has three acute angles and two sides that are
the same length.
2. Draw one triangle that has one right angle and no sides that are the
same length.
Collect the papers to review to ensure that all student responses
are correct.
Possible responses:
1.
2.
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