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If zinC lies on the circle whose equat...

If `zinC` lies on the circle whose equation is `|z-3i|=3sqrt2.` then the argument of `((z-3)/(z+3))` can be

A

`tan^(-1)3`

B

`(pi)/(2)`

C

`(pi)/(4)`

D

`tan^(-1)3sqrt2`

Text Solution

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The correct Answer is:
To solve the problem, we need to find the argument of the expression \(\frac{z - 3}{z + 3}\) where \(z\) lies on the circle defined by the equation \(|z - 3i| = 3\sqrt{2}\). ### Step-by-step Solution: 1. **Understanding the Circle**: The equation \(|z - 3i| = 3\sqrt{2}\) describes a circle in the complex plane centered at \(3i\) (which corresponds to the point \((0, 3)\) in the Cartesian plane) with a radius of \(3\sqrt{2}\). 2. **Expressing \(z\)**: Let \(z = x + iy\). The equation of the circle can be rewritten as: \[ |(x + iy) - 3i| = 3\sqrt{2} \implies |x + i(y - 3)| = 3\sqrt{2} \] This leads to: \[ \sqrt{x^2 + (y - 3)^2} = 3\sqrt{2} \] Squaring both sides gives: \[ x^2 + (y - 3)^2 = 18 \] 3. **Finding the Argument**: We need to find the argument of \(\frac{z - 3}{z + 3}\). First, we calculate \(z - 3\) and \(z + 3\): \[ z - 3 = (x - 3) + iy \] \[ z + 3 = (x + 3) + iy \] 4. **Using Argument Properties**: The argument of a quotient of complex numbers is the difference of their arguments: \[ \text{arg}\left(\frac{z - 3}{z + 3}\right) = \text{arg}(z - 3) - \text{arg}(z + 3) \] 5. **Calculating Each Argument**: Using the formula for the argument: \[ \text{arg}(a + ib) = \tan^{-1}\left(\frac{b}{a}\right) \] Thus, \[ \text{arg}(z - 3) = \tan^{-1}\left(\frac{y}{x - 3}\right) \] \[ \text{arg}(z + 3) = \tan^{-1}\left(\frac{y}{x + 3}\right) \] 6. **Finding the Difference**: Therefore, \[ \text{arg}\left(\frac{z - 3}{z + 3}\right) = \tan^{-1}\left(\frac{y}{x - 3}\right) - \tan^{-1}\left(\frac{y}{x + 3}\right) \] 7. **Using the Tangent Difference Formula**: We can use the tangent difference formula: \[ \tan^{-1}(a) - \tan^{-1}(b) = \tan^{-1}\left(\frac{a - b}{1 + ab}\right) \] Let \(a = \frac{y}{x - 3}\) and \(b = \frac{y}{x + 3}\). Then, \[ \text{arg}\left(\frac{z - 3}{z + 3}\right) = \tan^{-1}\left(\frac{\frac{y}{x - 3} - \frac{y}{x + 3}}{1 + \frac{y^2}{(x - 3)(x + 3)}}\right) \] 8. **Simplifying the Expression**: This simplifies to: \[ = \tan^{-1}\left(\frac{y\left(\frac{(x + 3) - (x - 3)}{(x - 3)(x + 3)}\right)}{1 + \frac{y^2}{(x - 3)(x + 3)}}\right) \] \[ = \tan^{-1}\left(\frac{6y}{(x - 3)(x + 3) + y^2}\right) \] 9. **Using the Circle Equation**: From the circle equation \(x^2 + (y - 3)^2 = 18\), we can substitute \(x^2 + y^2\) to find the final argument. 10. **Final Result**: After simplification, we find that the argument can take the value of \(\frac{\pi}{4}\). ### Conclusion: The argument of \(\frac{z - 3}{z + 3}\) can be \(\frac{\pi}{4}\).

To solve the problem, we need to find the argument of the expression \(\frac{z - 3}{z + 3}\) where \(z\) lies on the circle defined by the equation \(|z - 3i| = 3\sqrt{2}\). ### Step-by-step Solution: 1. **Understanding the Circle**: The equation \(|z - 3i| = 3\sqrt{2}\) describes a circle in the complex plane centered at \(3i\) (which corresponds to the point \((0, 3)\) in the Cartesian plane) with a radius of \(3\sqrt{2}\). 2. **Expressing \(z\)**: ...
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