12. Each figure below involves a rectangle and two semicircles. (Dashed lines are not part of a figure.) Write formulas for the
perimeter P and area A of each figure, and then rewrite the
formulas to express l in terms of the other variables and
constants in the formulas.
l
l
A.
B

Given:

To prove:

Solution:

The two-column proof is:

Statement                                        Reason

1.                            1. Given

2.                           2. Given

3.                                      3. Common side

4.                          4. ASA congruent postulate

5.                                     5. CPCTC

Hence proved.