In the complex plane ,the vertices of an equilateral triangle are represented by the complex numbers z1,z2 and z3 ,prove that 1z1z2+1z2z3+1z3z1=0?

1z1z2+1z2z3+1z3z1=0

1 Answer
Jan 3, 2018

See below.

Explanation:

Calling u=z1z2 with z1,z2 vertices of an equilateral triangle, the other two sides can be represented as

v=ueiϕ
w=ue2iϕ with ϕ=±23π (triangle can be reflected)
![https://www.geogebra.org/geometry](useruploads.socratic.org)
Now,

1u+1v+1w=1z1z2(1+eiϕ+e2iϕ)=1z1z2(e3iϕ1eiϕ1)

but the numerator

e3iϕ1=e±3i23π1=11=0 then finally

1u+1v+1w=0