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: 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