Solve the equation , expressing your answers in the form , where and .
, and are three of the roots of such that
- (i)
Find the smallest positive integer such that is real and positive.
- (ii)
The points and represent the roots and respectively in the Argand diagram. The line segment is obtained by rotating the line segment through clockwise about the point . Find the real part of the complex number represented by point , giving your answer in exact trigonometric form.
- (i)
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Worked solution
2[0](i)
1. Identify the roots $z_1$ and $z_2$ from the equation $z^5+32=0$.
Considering the roots with arguments in :
For ,
For ,
For ,
Since , we can deduce:
2. Find the ratio $\frac{z_1}{z_2}$ in exponential form.
3. Apply the condition for $\left(\frac{z_1}{z_2}\right)^n$ to be real and positive to find the smallest positive integer $n$.
For a complex number to be real and positive, its argument must be an integer multiple of :
To find the smallest positive integer , we substitute :
2[0](ii)
1. Identify the complex numbers $z_1$ and $z_3$ from the roots of $z^5+32=0$.
The roots are .
For roots with :
Given , we have and .
2. Formulate the relationship for a clockwise rotation by $\frac{\pi}{2}$ about point $B$.
A clockwise rotation of corresponds to multiplication by .
The vector is represented by , and is represented by .
Therefore,
3. Substitute $z_1$ and $z_3$ and convert to Cartesian form to solve for $z_{A'}$.
Using :
4. Extract the real part of $z_{A'}$.
The real part of is the component without the :
AI analysis — may contain mistakes.
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