Complex Loci Question

A sketch of the locus of a complex number z is shown above, determine the maximum value of arg(z) correct to two decimal places where 0\le z \le 2\pi

Draw tangent lines from the origin to the circle.

Remember tangent lines are perpendicular to the radii

The maximum argument is this angle

I am going to find the angle in two sections

From the diagram the radius of the circle is 2 and the centre is (4, 3). Hence the distance from the origin to the centre is 5.

    \begin{equation*}sin(\theta_1)=\frac{2}{5}\end{equation}

    \begin{equation*}\theta_1=0.412\end{equation}

    \begin{equation*}sin(\theta_2)=\frac{3}{5}\end{equation}

    \begin{equation*}\theta_2=0.644\end{equation}

Hence maximum arg(z)=1.06

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Filed under Complex Numbers, Right Trigonometry, Sketching Complex Regions, Trigonometry, Year 12 Specialist Mathematics

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