Hyperbola 2 Question 12

12. Tangents are drawn to the hyperbola x29y24=1, parallel to the straight line 2xy=1. The points of contacts of the tangents on the hyperbola are

(2012)

(a) 922,12

(b) 922,12

(c) (33,22)

(d) (33,22)

Passage Based Problems

The circle x2+y28x=0 and hyperbola x29y24=1 intersect at the points A and B.

(2010)

Show Answer

Answer:

Correct Answer: 12. (b)

Solution:

  1. PLAN Equation of tangent to x2a2y2b2=1 is y=mx±a2m2b2

Description of Situation If two straight lines

a1x+b1y+c1=0

and a2x+b2y+c2=0 are identical. Then, a1a2=b1b2=c1c2

Equation of tangent, parallel to y=2x1 is

y=2x±9(4)4y=2x±32

The equation of tangent at (x1,y1) is

xx19yy14=1

From Eqs. (i) and (ii),

or

x1=922,y1=12



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