120573 The equation of the ellipse having a vertex at (6,1) a focus at (4,1) and the eccentricity 35 is
B Given, vertex (6,1) and focus (4,1) e=35,SA=a−ae 2=a(1−e) Also, 2=a(1−e) 2=a(1−35) a=5 ∴b2=a2(1−e2)=25(1−925)=16Hence, the required equation (x−1)225+(y−1)216=1
120574 Find the equation of an ellipse whose vertices are (±5,0) and foci are (±4,0)
A Given, vertices (±5,0)=(±a,0) Foci (±4,0)=(±ae,0) ae=4 e=4a=45 ∴b2=a2(1−e2)=25(1−1625)=9 b=3 Hence, equation: x2a2+y2b2=1 x225+y29=1 9x2+25y2=225
120575 If α,β are the eccentric angles of the extremities of a focal chord (other than the major axis) of the ellipse x2+4y2−4 then 3cosα+β2=
A Given, x2+4y2−4=0 x24+y21=1 Eccentricity, e=1−b2a2=1−14 e=32 ∴ Focus =(3,0) Equation of required chord. xacos(α+β2)+ybsin(α+β2)=cos(α−β2) x2cos(α+β2)+y1sin(α+β2)=cos(α−β2) It passes through (3,0) 32cos(α+β2)=cos(α−β2) 3cos(α+β2)=2cos(α−β2)
120576 In the ellipse, if the distance between the foci is 6 units and the length of its minor axis is 8 units, then its eccentricity is
D Given, 2ae=6 And, minor axis 2 b=8 We known that, b2=a2(1−e2) (4)2=a2−a2e2 (4)2=a2−(3)2 a2=25 a=5 2ae=6 e=35 and ∴e=35