If CF is the perpendicular from the centre C f ellipse x2/a2+ y2/b2 = 1 on the tangent at any point P & G is the point when the normal at P meets the major axis , then CF PG equals to

(a) a2 (b) ab

(c) b2 (d) b3

plzz explain..!!

Question

If CF is the perpendicular from the centre C f ellipse x2/a2+ y2/b2 = 1 on the tangent at any point P & G is the point when the normal at P meets the major axis , then CF PG equals to

(a) a2 (b) ab

(c) b2 (d) b3

plzz explain..!!

M Murali Krishna · Answer

Equation of tangent at

P(a costhita, b sinthita) on ellipse is

(x costhita/a) + ( y sinthita/b) = 1.

i.e. bx costhita + ay sinthita = ab.

CF= ab/sqrt (b^2 cos^2thita + a^2 sin^2thita).

Equation of Normal at
P(a costhita, b sinthita) on ellipse is

ax/ costhita – by/ sinthita =a^2-b^2.

solving with y=0 we get G= ( (a^2-b^2) costhita /a, 0).

By distance formula, PG = (b/a)sqrt (b^2 cos^2thita + a^2 sin^2thita).

CF PG = b^ 2

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If CF is the perpendicular from the centre C f ellipse x2/a2+ y2/b2 = 1 on the tangent at any point P & G is the point when the normal at P meets the major axis , then CF PG equals to (a) a2 (b) ab (c) b2 (d) b3 plzz explain..!!

If CF is the perpendicular from the centre C f ellipse x2/a2+ y2/b2 = 1 on the tangent at any point P & G is the point when the normal at P meets the major axis , then CF PG equals to

(a) a2 (b) ab

(c) b2 (d) b3

plzz explain..!!

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