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A complex number $z$ lies on the unit circle in the complex plane, as shown in the diagram - HSC - SSCE Mathematics Extension 2 - Question 3 - 2023 - Paper 1

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A complex number $z$ lies on the unit circle in the complex plane, as shown in the diagram. Which of the following complex numbers is equal to $ar{z}$ ? A. $-z$ B... show full transcript

Worked Solution & Example Answer:A complex number $z$ lies on the unit circle in the complex plane, as shown in the diagram - HSC - SSCE Mathematics Extension 2 - Question 3 - 2023 - Paper 1

Step 1

Determine $ar{z}$

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Answer

Given that zz lies on the unit circle, we know that the conjugate of zz, denoted as ar{z}, is represented as follows:

ar{z} = e^{-i heta}

where heta heta is the angle corresponding to zz. This is due to the property of complex numbers on the unit circle.

Step 2

Identify $z$ based on given angle

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Answer

From the diagram, it can be observed that the angle corresponding to zz is rac{ heta}{3}, leading to:

z = e^{i rac{ heta}{3}}

Step 3

Consider $z^2$

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Answer

We can express z2z^2 as:

z^2 = ig(e^{i rac{ heta}{3}}ig)^2 = e^{i rac{2 heta}{3}}

Step 4

Express $ar{z}$ in terms of $z^2$

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Answer

Now, considering the conjugate once again:

ar{z} = e^{-i rac{ heta}{3}} = -z^2

Step 5

Final Answer

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Answer

Thus, the complex number that is equal to ar{z} is:

B. z2-z^2

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