If is the angle subtended at by the circle

MATHEMATICS · Single correct · CBSE · Mathematics · Conic Sections · Conic Sections

Problem

If α\alpha is the angle subtended at P(x1,y1)P(x_1, y_1) by the circle S≡x2+y2+2gx+2fy+c=0S \equiv x^2 + y^2 + 2gx + 2fy + c = 0 , then (1) cot⁡α=S1g2+f2−c\cot \alpha = \frac{\sqrt{S_1}}{\sqrt{g^2 + f^2 - c}} (2) cot⁡α2=S1g2+f2−c\cot \frac{\alpha}{2} = \frac{\sqrt{S_1}}{\sqrt{g^2 + f^2 - c}} (3) tan⁡α=2g2+f2−cS1\tan \alpha = \frac{2\sqrt{g^2 + f^2 - c}}{\sqrt{S_1}} (4) α=2tan⁡−1(g2+f2−cS1)\alpha = 2 \tan^{-1} \left( \frac{\sqrt{g^2 + f^2 - c}}{\sqrt{S_1}} \right)

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