standard_description: Use informal arguments to establish facts about the angle sum and exterior angle of triangles, about the angles created when parallel lines are cut by a transversal, and the angle-angle criterion for similarity of triangles. For example, arrange three copies of the same triangle so that the sum of the three angles appears to form a line, and give an argument in terms of transversals why this is so.
problem_activity: Narrative
The purpose of this activity is for students to use informal language and the structure of the coordinate grid to describe a given shape. Some questions may be about properties of the shape rather than its location. For example, “Is the rectangle wider than it is tall?” is a question that eliminates many shapes. As the number of shapes decreases, the location will become more important and the features of the coordinate grid will play a larger role. The synthesis gives students an opportunity to consider how the numbers in the coordinate grid can be useful to accurately describe the attributes, location, and orientation of a given shape (MP6).
Launch
Groups of 2
Activity
5 minutes: partner work time
Monitor for students who:
reference the structure of the grid in their questions
reference the numbers on the horizontal and vertical axes in their questions
use gestures to indicate horizontal or vertical gridlines
use the words horizontal or vertical
Student Facing
Play a round of Guess Which One.
Sit next to your partner.
Partner A:
Mentally choose a shape card without indicating which shape card you chose.
Partner B:
Ask yes or no questions to determine which shape card partner A has chosen.
A
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B
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C
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D
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E
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F
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G
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H
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I
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J
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K
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L
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Switch roles and play another round of Guess Which One.
Diego and Kiran were playing a round of Guess Which One. These are the last two shapes. What question can Kiran ask to determine which shape is the one that Diego picked?
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Student Response
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Advancing Student Thinking
If students do not reference the grid lines or numbers when asking questions, refer to the display from the first activity and ask, “Which words can you use to help you figure out which shape your partner chose?”
Activity Synthesis
Ask previously identified students to share their reasoning.
“How do the numbers help us locate shapes on the grid?” (I could use them to describe the lines and the points. I could also use numbers to describe the location of the shape: “Go up three. Go over 5.”)
“The gridlines with numbers on them are called
axes
. The coordinate grid has a
horizontal axis
and a
vertical axis
.”


aligns: no