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#1 Re: Help Me ! » tangent planes » 2008-04-23 01:10:28

Differentiate....then evaluate both at 1,2,3 see if that helps

#2 Help Me ! » extrema » 2008-04-22 16:49:55

dexza666
Replies: 3

find all critical points of
f(x, y)=e^x(1-cos y)

and classify these critical points.

#3 Help Me ! » tangent plane » 2008-04-22 16:09:23

dexza666
Replies: 1

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Two surfaces are said to be orthogonal at a point P if the normals to their tangent planes are perpendicular at P. Show that the surfaces z= 1/2(x²+y² -1) and z=1/2(1- x²-y²) are orthogonal at all points of intersection.

#4 Help Me ! » chain rule » 2008-04-22 12:04:29

dexza666
Replies: 2

Let f = f(u,v) and u = x + y, v = x - y

i) assume f to be twice differentiable and compute f_{xx} and f_{yy} in terms of f_{u}, f_{v}, f_{uu}, f_{uv} and f_{vv}.

ii)express the wave equation:

((∂²f)/(∂x²))-((∂²f)/(∂y²))=0

in terms of partial derivatives of f with respect to u and v.

#5 Re: Help Me ! » local linearization » 2008-04-22 11:46:43

The first answer was the right way of doing it. im not sure about thia local quadraticisation

#6 Help Me ! » tangent planes » 2008-04-22 11:39:12

dexza666
Replies: 4

Two surfaces are said to be tangential at a point P if they have the same tangent plane at P . Show that the surfaces                      z = √(2x²+2y²-1) and z = (1/3)√(x²+y²+4) are tangential at the point (1, 2, 3).

#7 Help Me ! » more local linearization » 2008-04-22 00:18:49

dexza666
Replies: 2

find the local linearization of the function f(x,y) = √(x³+y4) at the point (1,2). use it to estimate f(1.04,1.98).

#8 Help Me ! » local linearization » 2008-04-21 23:19:09

dexza666
Replies: 3

An unevenly heated plate has temperature T(x,y) in degrees celcius at the point (x,y). If T(2,1)=135, and Tx(2,1)=16 and Ty(2,1)= -15, estimate the temperature at the point (2.04, 0.97).

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