standard_description: Derive the formula A = 1/2 ab sin(C) for the area of a triangle by drawing an auxiliary line from a vertex perpendicular to the opposite side.
problem_activity: Narrative
The purpose of this Choral Count is to invite students to count on from a number other than 1. This helps students develop fluency with the count sequence and will be helpful as students relate counting to addition and begin to make sense of the counting on method of adding.
Launch
"Count by 1, starting at 10."
Record as students count.
Stop counting and recording at 40.
Activity
"What patterns do you see?"
1–2 minutes: quiet think time
Record responses.
Student Response
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Activity Synthesis
"How did you know what number comes after 10? 19? 29?"


aligns: no