standard_description: Prove theorems about parallelograms. Theorems include: opposite sides are congruent, opposite angles are congruent, the diagonals of a parallelogram bisect each other, and conversely, rectangles are parallelograms with congruent diagonals.
problem_activity: Activity
In this activity students use trigonometry to calculate the measure of an angle when given two sides of a right triangle. Then they apply a method of their choosing to calculate other side lengths and angle measures in the triangle.
Monitor for students who use:
the Pythagorean Theorem
multiple trigonometric equations
the Triangle Angle Sum Theorem
Launch
“Don’t forget to calculate 3 measurements per triangle.”
Students need not complete all the problems before the discussion.
Engagement: Provide Access by Recruiting Interest.
Leverage choice around perceived challenge. Invite students to select 2 of the 3 questions to complete. Chunking this task into more manageable parts may also support students who benefit from additional processing time.
Supports accessibility for: Organization; Attention; Social-emotional skills
Student Facing
Find all missing side and angle measures.
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Student Response
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Activity Synthesis
Tell students there are at least 3 different methods for solving these problems:
Pythagorean Theorem
multiple trigonometric equations
the Triangle Angle Sum Theorem
Invite students to rank the methods in order of most to least preferred and tell them to be prepared to share their reasoning. After 1 minute of quiet think time ask a few students to share. Tell the class that there is no one best method; personal preference and the specific problem both influence your choices.
Speaking: MLR8 Discussion Supports.
To support students in producing statements about the methods they preferred for solving the problems, provide sentence frames for students to use when they share. For example, “I prefer _____ because _____,” or  “_____ was better because _____.”
Design Principle(s): Support sense-making


aligns: no