Complex numbers and area

[forest coral]

I'm really stuck on how to even begin part A, does anyone know how to go about this?

[opaque sequoia]

do you know any rule for the area ?

[noble gate]

Try to use this definition:

[noble gate]

Additionally I'd define:

$\a := x_a + iy_a \
b := x_b + iy_b \
c := x_c + iy_c\$

and then work from there!