The number of complex numbers z, satisfying |z|=1 and | z z+ zz |=1, is :
- 8
- 10
- 4
- 6
Answer
(1) 8
Solution
|z|=1 means z lies on the unit circle: z=ei .
z z+ zz=2 2 |2 2 |=1 2 = 12
[figure]
2 [0,4 ) covers two turns: 2 = 12 gives 4 points, 2 =- 12 gives 4 points.
8 points ( =30 ,60 ,120 , ,330 )
Answer: (1)