Question

Are there two pair of directrix in ellipse, giving a total of 4?

Answer 1

no only 2 directrices

Answer 2

THERE ARE TWO AND IF U INTERCHANGE A AND B THEN AGAIN TWO..

Answer 3

the minor axis doesnt correspond to directrices

Answer 4

why the minor axis doesnt correspond to directrices???

Answer 5

sorry to say only major axis has dirextrix..

Answer 6

directrix is a line perpendicular to the axis of symmetry i parabola, n perpendicular to major axis in ellipse

Answer 7

that means foci can only be on major axis and never on minor axis?

Answer 8

actually directrix is the locus of that points where the two tangent of a curve meet perpendicularly...

Answer 9

yes foci...is always in major axis...

Answer 10

not strictly dipankar

Answer 11

by definition, elllipse is the locus of all those points the sum of whose distance from a fixed point n a fixed line is constant, the fixed point is focus and the fixed line is directrix

Answer 12

why??? can u xplain??

Answer 13

uzma's right

Answer 14

the axia on which foci lie is called major axis by definition

Answer 15

i mean the director circle of a circle is the locus of pts where tangents meet perpendicularly

Answer 16

@uzma
"by definition, elllipse is the locus of all those points the sum of whose distance from a fixed point n a fixed line is constant, the fixed point is focus and the fixed line is directrix"

it should be noted that the ratio is const. and not the sum!

Answer 17

yes..and that ratio is eccentricity

Answer 18

oh, yes my mistake

Answer 19

sum of distances from foci is constant and equal to 2a

Answer 20

the sum of the distance from two fixed point is constant

Answer 21

right @ him

Answer 22

what will be the radius of the director circle for a circle of radius r. BTW I am hearing this word "director circle" first time from dipankar...

Answer 23

director circle?

Answer 24

yes...director circle..

Answer 25

the equation of director circle for an ellipse is x^2+y^2=a^2+b^2
and that for hyperbola is x^2+y^2=|a^2-b^2|

Answer 26

In geometry, the director circle of an ellipse or hyperbola (also called the orthoptic circle or Fermat–Apollonius circle) is a circle formed by the points where two perpendicular tangent lines to the curve cross.

Answer 27

chutzpah..is it clear now??

Answer 28

@dipankar
i came across this term, "director circle" for the first time and i m thankful to u for upgrading my knowledge. u seem to be a knowledge tank for me. i'd like to know where and what r u studying....

Answer 29

i'm from india...i study engineering..electronics and telecommunication..

Answer 30

what about u??

Answer 31

in which college and yr.?