standard_description: Prove the addition and subtraction formulas for sine, cosine, and tangent and use them to solve problems.
problem_activity: Problem 1
Find the following products.
a.   20 × 4
b.   9 × 300
c.   5 × 6,000
Problem 2
Estimate the following products.
a.   8 × 84
b.   458 × 4
c.   2 × 9,340


aligns: no