December 15th, 2013, 04:00 AM  #1 
Member Joined: Nov 2012 Posts: 61 Thanks: 0  parabola
Tangents are drawn from (4,0) to . Radius of circles that would touch these tangents and corresponding chord of contact, can be equal to 
December 15th, 2013, 10:42 AM  #2 
Global Moderator Joined: Dec 2006 Posts: 18,686 Thanks: 1522 
If tangent is y = m(x + 4), m²(x + 4)² = 16x has a repeated root (zero discriminant), so (8m²  16)²  64m^4 = 0, which implies m = ±1. The points of contact are (4, ±, so the chord of contact has equation x = 4. Can you now show that the circle's radius can be 8(?2 + 1)? Quick followup question: what integer value, if any, can the radius have? 

Tags 
parabola 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
Parabola  Arley  Algebra  10  April 28th, 2012 12:19 PM 
What is this? (Parabola?)  boomer029  Algebra  10  January 11th, 2012 05:35 PM 
Parabola  new york mafia  Calculus  3  August 8th, 2009 02:56 PM 
Parabola  Sean  Algebra  2  January 11th, 2007 08:39 PM 
Parabola help please?  Bloo  Economics  0  December 31st, 1969 04:00 PM 