In a rectangular coordinate system, what is the area of a triangle whose vertices have the coordinates (2, 0), (6, 3), and (6, -3)?
Choose the correct choice:  A) 11  B) 12  C) 13  D) 14  E) 15
The triangle is symmetric about the x-axis.   The part above the x-axis forms a triangle with a base of 4 and a height of 3.   The area of this part is (1/2)(4)(3).   We can double this to find the area of the whole triangle.   The total area is (2)(1/2)(4)(3) = 12.   The answer is 12.
<result>B</result>
In a rectangular coordinate system, what is the area of a triangle whose vertices have the coordinates (2, 0), (6, 3), and (6, -3)?