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AP EAMCET · Maths · Ellipse

If S and S' are the focii of an ellipse, B is one end of the minor axis and SBS'=90°, then the eccentricity of that ellipse is

  1. A 32
  2. B 74
  3. C 12
  4. D 12
Verified Solution

Answer & Solution

Correct Answer

(C) 12

Step-by-step Solution

Detailed explanation

Let the coordinates of the focii of an ellipses are Sae,0 and S'-ae,0. Since, ∠SBS'=90 ∴SS'2=SB2+S'B2 2ae2=ae-02+0-b22+-ae-02+0-b22 ⇒2ae2=ae2+b2+ae2+b22 ⇒4a2e2=2a2e2+2b2 ⇒2a2e2=2b2 ⇒b2a2=e2  ...i Also, e2=1-b2a2…