N narrowpin Member Joined Jan 6, 2007 Messages 108 Gender Male HSC 2008 Oct 26, 2008 #1 dumb question, but how do you find the focus and directrix of the hyperbola xy=c^2 Last edited: Oct 26, 2008
duy.le Member Joined Feb 15, 2007 Messages 135 Gender Male HSC 2008 Oct 26, 2008 #2 u move the old focus through 45 degrees anticlockwise. keep the modulus and use trig.
Q qqmore Member Joined Feb 8, 2007 Messages 78 Gender Undisclosed HSC 2008 Oct 26, 2008 #3 For xy = 1/2 a^2 The focus is (a,a) ; (-a,-a) Directices: x + y = a and x + y = -a Eccentricity is always rt 2 so for xy=c^2 focus is ( rt 2 c ,rt c ) and ( -rt 2 c, - rt 2 c) ... just memorise it
For xy = 1/2 a^2 The focus is (a,a) ; (-a,-a) Directices: x + y = a and x + y = -a Eccentricity is always rt 2 so for xy=c^2 focus is ( rt 2 c ,rt c ) and ( -rt 2 c, - rt 2 c) ... just memorise it
