Question regarding complex numbers

[Mohsin Hussain]

1)If a= cosα + i sinα and the equation az² + az +1 =0 has a pure imaginary root, then tanα=?

2) cosα+isinα=e^iα , quadratic formula

3) What i tried to do was,i put a constant real number and tried to solve it and used demoivres theorem, although the answer is getting weirder and weirder.

 

[PeroK]

You need to show your work.

 

[Mark44]

You need to show your work.

Yes, please show what you have done, Mohsin Hussain.

This is an important piece of information --

the equation az² + az +1 =0 has a pure imaginary root

 

[Mohsin Hussain]

sorry for bothering, it was a fairly easy one. didnt read the word "purely". Thanks.