What is the area of a triangle with vertices at (0,0), (3,1), and (1,5)?
Correct: C
The area of a triangle with vertices (0,0), (x1,y1), and (x2,y2) is given by |(x1y2 - x2y1)/2|. In this case, the area is |(3*5 - 1*1)/2| = |(15 - 1)/2| = |14/2| = 7.