Core Logic
Intersection of circle with x-axis provides A(2,0)$A(2,0)$ and B(-2,0)$B(-2,0)$.
Let the point of intersection of AQ$AQ$ and BP$BP$ be R(h, k)$R(h, k)$.
Since R$R$ lies on BP$BP$, the slope mBR = mBP$m_{BR} = m_{BP}$:
(k)/(h + 2) = (2 α)/(2 α + 2) = (α)/(2)$$\frac{k}{h + 2} = \frac{2\sin\alpha}{2\cos\alpha + 2} = \tan\frac{\alpha}{2}$$
Since R$R$ lies on AQ$AQ$, the slope mAR = mAQ$m_{AR} = m_{AQ}$:
(k)/(h - 2) = (2 β)/(2 β - 2) = ( β)/( β - 1) = - (β)/(2)$$\frac{k}{h - 2} = \frac{2\sin\beta}{2\cos\beta - 2} = \frac{\sin\beta}{\cos\beta - 1} = -\cot\frac{\beta}{2}$$
Execution
We are given α - β = (π)/(2) ⇒ (α)/(2) - (β)/(2) = (π)/(4)$\alpha - \beta = \frac{\pi}{2} \Rightarrow \frac{\alpha}{2} - \frac{\beta}{2} = \frac{\pi}{4}$.
Applying the (A-B)$\tan(A-B)$ formula:
((α)/(2) - (β)/(2)) = ( (α)/(2) - (β)/(2))/(1 + (α)/(2) (β)/(2)) = 1$$\tan\left(\frac{\alpha}{2} - \frac{\beta}{2}\right) = \frac{\tan\frac{\alpha}{2} - \tan\frac{\beta}{2}}{1 + \tan\frac{\alpha}{2}\tan\frac{\beta}{2}} = 1$$
Substitute the slope relations:
(α)/(2) = (k)/(h+2)$\tan\frac{\alpha}{2} = \frac{k}{h+2}$
(β)/(2) = -(h-2)/(k)$\tan\frac{\beta}{2} = -\frac{h-2}{k}$ (since - (β)/(2) = (k)/(h-2)$-\cot\frac{\beta}{2} = \frac{k}{h-2}$)
1 = ((k)/(h+2) + (h-2)/(k))/(1 + ((k)/(h+2))((2-h)/(k)))$1 = \frac{\frac{k}{h+2} + \frac{h-2}{k}}{1 + \left(\frac{k}{h+2}\right)\left(\frac{2-h}{k}\right)}$
1 = k² + h² - 4(k(h+2))/(k) · (k(h+2) - k(2-h))/(k(h+2)) wait, clear denominator$1 = \frac{k^2 + h^2 - 4}{\frac{k(h+2)}{k} \cdot \frac{k(h+2) - k(2-h)}{k(h+2)} \dots \text{ wait, clear denominator}}$
1 = (k² + h² - 4)/(k(h+2) + k(2-h)) × k(h+2)$1 = \frac{k^2 + h^2 - 4}{k(h+2) + k(2-h)} \times k(h+2) \dots$
The denominator simplifies to:
1 + (2-h)/(h+2) = (h+2+2-h)/(h+2) = (4)/(h+2)$$1 + \frac{2-h}{h+2} = \frac{h+2+2-h}{h+2} = \frac{4}{h+2}$$
Numerator is (k² + h² - 4)/(k(h+2))$\frac{k^2 + h^2 - 4}{k(h+2)}$.
So the expression simplifies to:
1 = (k² + h² - 4)/(4k)$$1 = \frac{k^2 + h^2 - 4}{4k}$$
h² + k² - 4k - 4 = 0$$h^2 + k^2 - 4k - 4 = 0$$
Locus of R$R$ is x² + y² - 4y - 4 = 0$x^2 + y^2 - 4y - 4 = 0$.
Pattern Recognition
Connecting chords from extreme diameter vertices to points whose parametric angles differ by π/2$\pi/2$ reliably generates perpendicular-like slope products or standard tangent angle identities, mapping directly to a circular locus.
Chapter Mix
Class 11 Maths: Circles