Cross product and Heron's formula

Why when do I use the cross product to get the area of a triangle I get the right answer when I use Heron's formula I get the wrong answer that is off by 11%?

The question is found below;

**17.** Given the points A(1, 2, 0), B(0, 1, 0) and C(1, 0, 2), determine the area of triangle ABC.

The answer is 3^0.5 . With Heron's formula I get 1.93649. Why do they conflict?

EDIT: Never mind, I forgot to find BC. LoL, I had AC, CA, and AB, but no BC. I knew something was up. :P