If z1, z2, z3 C are the vertices of an equilateral triangle whose centroid is z0, then k=13 (zk - z0)2 is equal to
- 0
- 1
- i
- -i
Answer
(1) 0
Solution
For an equilateral triangle the centroid is also the circumcentre, and the vertices are obtained from one another by a rotation of 2 3 about z0:
z1 - z0 = a, z2 - z0 = a , z3 - z0 = a 2 ( = cube root of unity)
k=13 (zk - z0)2 = a2(1 + 2 + 4)
= a2(1 + 2 + )
= 0
Answer: (1)