Thread: Complex- area enclosed by a polygon

So take the limit of bar zk(z_k+1-z_k)
which will end up being 1/2[zk+z_k+1](z_k+1-zk}
1/2[zk+1^2-zk^2}
1/2[zn^2-z1^2]
1/2(b^2-a^2)