Related Formula
For a complex number z = x + iy$z = x + iy$:
- |z| = √(x² + y²)$|z| = \sqrt{x^2 + y^2}$
- z + z = 2x$z + \overline{z} = 2x$
- z - z = 2iy$z - \overline{z} = 2iy$
Core Logic
Let z = x + iy$z = x + iy$.
The first condition |z - 1| = 1$|z - 1| = 1$ describes a circle:
(x-1)² + y² = 1 (1)$$(x-1)^{2} + y^{2} = 1 \quad \implies (1) $$
The second condition gives a straight line:
(√(2)-1)(2x) - i(2iy) = 2√(2)$$(\sqrt{2}-1)(2x) - i(2iy) = 2\sqrt{2}$$
2(√(2)-1)x + 2y = 2√(2)$$2(\sqrt{2}-1)x + 2y = 2\sqrt{2}$$
(√(2)-1)x + y = √(2) (2)$$(\sqrt{2}-1)x + y = \sqrt{2} \quad \implies (2) $$
The set S$S$ contains the intersection points of this circle and line.
Step 1: Solve for Intersection Points
From (2), y = √(2) - (√(2)-1)x$y = \sqrt{2} - (\sqrt{2}-1)x$. Substitute this into (1):
(x-1)² + [√(2) - (√(2)-1)x]² = 1$$(x-1)^2 + [\sqrt{2} - (\sqrt{2}-1)x]^2 = 1$$
Solving this quadratic equation gives two values of x$x$:
x = 1 or x = 12-√(2)$$x = 1 \quad \text{or} \quad x = \frac{1}{2-\sqrt{2}} $$
- Case A: x = 1 y = √(2) - (√(2)-1)(1) = 1$x = 1 \implies y = \sqrt{2} - (\sqrt{2}-1)(1) = 1$.
So, one point is zA = 1 + i$z_A = 1 + i$.
Its magnitude is |zA| = √(1² + 1²) = √(2)$|z_A| = \sqrt{1^2 + 1^2} = \sqrt{2}$.
- Case B: x = 12-√(2) = 2+√(2)2 = 1 + 1√(2)$x = \frac{1}{2-\sqrt{2}} = \frac{2+\sqrt{2}}{2} = 1 + \frac{1}{\sqrt{2}}$.
Then y = √(2) - (√(2)-1)(1+ 1√(2)) = √(2) - (√(2) + 1 - 1 - 1√(2)) = 1√(2)$y = \sqrt{2} - (\sqrt{2}-1)\left(1+\frac{1}{\sqrt{2}}\right) = \sqrt{2} - \left(\sqrt{2} + 1 - 1 - \frac{1}{\sqrt{2}}\right) = \frac{1}{\sqrt{2}}$.
So, the other point is zB = (1 + 1√(2)) + i√(2)$z_B = \left(1 + \frac{1}{\sqrt{2}}\right) + \frac{i}{\sqrt{2}}$.
Its magnitude is |zB| = (1+ 1√(2))² + ( 1√(2))² = 1 + √(2) + (1)/(2) + (1)/(2) = 2 + √(2)$|z_B| = \sqrt{\left(1+\frac{1}{\sqrt{2}}\right)^2 + \left(\frac{1}{\sqrt{2}}\right)^2} = \sqrt{1 + \sqrt{2} + \frac{1}{2} + \frac{1}{2}} = \sqrt{2 + \sqrt{2}}$.
Step 2: Evaluate Min and Max Magnitude Expressions
Comparing magnitudes, |zB| > |zA|$|z_B| > |z_A|$, so:
z₁ = zB = (1 + 1√(2)) + i√(2)$$z_1 = z_B = \left(1 + \frac{1}{\sqrt{2}}\right) + \frac{i}{\sqrt{2}} $$
z₂ = zA = 1 + i$$z_2 = z_A = 1 + i $$
Now, calculate |√(2)z₁-z₂|²$|\sqrt{2}z_{1}-z_{2}|^{2}$:
√(2)z₁ = √(2)(1 + 1√(2)) + √(2)( i√(2)) = (√(2) + 1) + i$$\sqrt{2}z_1 = \sqrt{2}\left(1 + \frac{1}{\sqrt{2}}\right) + \sqrt{2}\left(\frac{i}{\sqrt{2}}\right) = (\sqrt{2} + 1) + i$$
√(2)z₁ - z₂ = (√(2) + 1 + i) - (1 + i) = √(2)$$\sqrt{2}z_1 - z_2 = (\sqrt{2} + 1 + i) - (1 + i) = \sqrt{2} $$
|√(2)z₁ - z₂|² = |√(2)|² = 2$$|\sqrt{2}z_1 - z_2|^2 = |\sqrt{2}|^2 = 2 $$
Pattern Recognition
Sees: Geometric constraint mapping to a circle and line intersection in the complex plane.
Shortcut: Rationalizing terms like 12-√(2)$\frac{1}{2-\sqrt{2}}$ immediately into standard form 1+ 1√(2)$1+\frac{1}{\sqrt{2}}$ saves you from handling layered fraction algebra down the line.
Chapter Mix
Class 11 Complex Numbers: Geometry
Class 10 Coordinate Geometry: Lines and Circles