Find the area of the triangles with vertices listed, first by finding the area of the rectangle enclosing the triangle and
subtracting the area of the surrounding triangles, then by using the formula
1 / 2 (x1y2 − x2y1).
a. , 0), , 6), , 1)
b. , 0), , 2), (−2, 6)
c. , 0), , −3), −2, 6)