standard_description: Prove the Laws of Sines and Cosines and use them to solve problems.
problem_activity: Narrative
The purpose of this Number Talk is to elicit strategies and understandings students have for adding on to 10. These understandings help students develop fluency and will be helpful later in this lesson when students write equivalent expressions.
Launch
Display one expression.
“Give me a signal when you have an answer and can explain how you got it.”
1 minute: quiet think time
Activity
Record answers and strategy.
Keep expressions and work displayed.
Repeat with each expression.
Student Facing
Find the value of each expression mentally.
\(7 + 10\)
\(7 + 2 + 8\)
\(10 + 9\)
\(4 + 9 + 6\)
Student Response
Teachers with a valid work email address can
click here to register or sign in
for free access to Student Response.
Activity Synthesis
“Why did some of the expressions have the same value?”


aligns: no