
Math General Math Forum  For general math related discussion and news 
 LinkBack  Thread Tools  Display Modes 
December 8th, 2016, 09:20 AM  #1 
Newbie Joined: Dec 2016 From: Tr Posts: 2 Thanks: 0  Curve equation ?
I am asked to write the equation of the curve which lies above the line y=2x and lies on the surface z=x^2+y^2 But this question seems not clear and proper. Because y=2x is a line in two dimensions and z=x^2+y^2 is the surface which is in 3 dimensional space. However, at least I should find curve equation which meets these conditions. I am really confused. btw, I should also represent this equation as w=f(x,y,z) function because after that I am going to find normal vector and tangent vector of that curve equation at some (x,y,z) point such as (1,2,5) 
December 8th, 2016, 02:55 PM  #2 
Global Moderator Joined: Dec 2006 Posts: 18,034 Thanks: 1393 
(y, z) = (2x, 5x²) or (y  2x)² + (z  5x²)² = 0.

December 21st, 2016, 08:00 AM  #3  
Math Team Joined: Jan 2015 From: Alabama Posts: 2,714 Thanks: 697  Quote:
In order that (x, 2x, z) lie on $\displaystyle z= x^2+ y^2$, we must have $\displaystyle z= x^2+ (2x)^2= 5x^2$. So these points are of the form $\displaystyle (x, 2x, 5x^2)$. Quote:
Last edited by Country Boy; December 21st, 2016 at 08:18 AM.  

Tags 
curve, equation 
Thread Tools  
Display Modes  

Similar Threads  
Thread  Thread Starter  Forum  Replies  Last Post 
looking for an equation of a curve  jamesraymond  Math  2  November 6th, 2016 11:33 PM 
equation of curve  AdityaDevN  Geometry  0  November 23rd, 2014 07:28 AM 
The Equation of a Tangent to a Curve  bilano99  Calculus  2  August 5th, 2013 05:10 AM 
BSpline curve equation  optikalefx  Algebra  0  October 24th, 2011 10:35 PM 
Scurve equation  Emmar01  Algebra  4  August 14th, 2007 06:04 AM 