My Math Forum  

Go Back   My Math Forum > High School Math Forum > Algebra

Algebra Pre-Algebra and Basic Algebra Math Forum


Reply
 
LinkBack Thread Tools Display Modes
November 15th, 2010, 01:28 PM   #1
Senior Member
 
Joined: Apr 2009

Posts: 106
Thanks: 0

Parabola and Directrix and Focus, Oh MY!!!

For the parabola y = x^2

I have determined that the focus is the point (0, 1/4)

I have determined that the directrix is the line y = -1/4

Am I correct?
julian21 is offline  
 
November 15th, 2010, 01:48 PM   #2
Senior Member
 
MarkFL's Avatar
 
Joined: Jul 2010
From: St. Augustine, FL., U.S.A.'s oldest city

Posts: 12,211
Thanks: 521

Math Focus: Calculus/ODEs
Re: Parabola and Directrix and Focus, Oh MY!!!

Yes, that is correct.

For the parabola whose axis of symmetry is the y-axis and whose vertex is at the origin,i.e the focus will be at and the directrix will be the line , which can be found using the definition of the parabola, i.e., the locus of all points being equidistant from a fixed line, the directrix, and a fixed point not on the line, the focus.
MarkFL is offline  
February 21st, 2013, 09:00 PM   #3
Banned Camp
 
Joined: Feb 2013

Posts: 224
Thanks: 6

Re: Parabola and Directrix and Focus, Oh MY!!!

Quote:
Originally Posted by julian21
For the parabola y = x^2

I have determined that the focus is the point (0, 1/4)

I have determined that the directrix is the line y = -1/4

Am I correct?
Whether something is correct depends on HOW you determine it. Did you read it in a book? Saw it on Youtube? Your classmate pass you a note during a quiz? You determine if something is correct by DOING it. CONSTRUCT the parabola, like this.

http://www.flickr.com/photos/85937466@N ... hotostream

or this

http://quadrivium.info/GGB/ParabRhombus.html
long_quach is offline  
Reply

  My Math Forum > High School Math Forum > Algebra

Tags
directrix, focus, parabola



Search tags for this page
Click on a term to search for related topics.
Thread Tools
Display Modes


Similar Threads
Thread Thread Starter Forum Replies Last Post
Equation of ellipse from directrix and focus daigo Algebra 1 July 5th, 2012 08:03 PM
Finding equation of parabola with focus and directrix daigo Algebra 3 July 5th, 2012 09:44 AM
sideways parabola?? find the directrix focus no calculus?? iloatheparabolas Elementary Math 1 August 9th, 2008 10:38 AM
sideways parabola?? find the directrix focus no calculus?? iloatheparabolas Abstract Algebra 0 August 8th, 2008 12:10 PM
directrix & focus of 'sideways' parabola w/o calculus? iloatheparabolas Algebra 0 August 7th, 2008 03:34 PM





Copyright © 2019 My Math Forum. All rights reserved.