# A few complex number qs (1 Viewer)

#### 5uckerberg

##### Well-Known Member
For d when you have this implies that you need to double the argument to obtain the arg of z so in turn

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Thus,

#### =)(=

##### Active Member
I got that but in the solution for some reason they also drew in (-2pi/3)

#### yanujw

##### Active Member
I got that but in the solution for some reason they also drew in (-2pi/3)
This is because squaring complex nos with arg (-2pi/3) gives them an arg of -4pi/3, which is an equilvalent arg to 2pi/3 and therefore satisfies the condition.

• =)(=

#### =)(=

##### Active Member
ohh okay I see but how would you get that working from pi/3

#### 5uckerberg

##### Well-Known Member
De Moivre's Theorem that is what is happening squaring the angle doubles the angle of rotation and so on.

• =)(=

#### =)(=

##### Active Member
I still can't see it for some reason

#### 5uckerberg

##### Well-Known Member
Part b well we need to know this fact and and
Once this is known our next step is pretty straightforward.

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I would like @=)(= to confirm the answer for this one.

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#### =)(=

##### Active Member
Part b well we need to know this fact and and
Once this is known our next step is pretty straightforward.

.

.

I would like @=)(= to confirm the answer for this one.