# Difference between Tangent Plane and Linearization

1. Jul 30, 2011

### newyorkcity

What is the difference?

According to my text...

Tangent Plane:

z-z0=fx(x0,y0)(x-x0) + fy(x0,y0)(y-y0)

Linearization:

L(x,y) = f(a,b) + fx(a,b)(x-a) + fy(a,b)(y-b)

2. Jul 30, 2011

### newyorkcity

What is the difference?

According to my text...

Tangent Plane:

z-z0=fx(x0,y0)(x-x0) + fy(x0,y0)(y-y0)

Linearization:

L(x,y) = f(a,b) + fx(a,b)(x-a) + fy(a,b)(y-b)

3. Jul 30, 2011

### anonymity

Well, think back to 2-dimensions.

What is the difference between a tangent line and a 2d linearization?

It is exactly the same concept, except brought into R3. Just as a 2-d linearization is a predictive equation based on a tangent line which is used to approximate the value of a function, a 3-d linearization is a predictive equation based on a tangent plane which is used to approximate a function.

4. Jul 30, 2011

### newyorkcity

Looking back at the text, I just missed the relationship between (a,b), (x0,y0), and (x,y). To clarify, the 'Tangent Plane' equation is used to find the tangent plane at a point P(x0,y0,z0). The 'Linearization' equation yields the linear approximation of f(x,y) at (a,b). Thanks for your help.

5. Jul 31, 2011

### HallsofIvy

Yes, just as the "linearization" of y= f(x) gives the tangent line to the curve, so the "linearization" of z= f(x,y) gives the tangent plane to the surface. The only difference is that when you talk about the "linearization" you are thinking of the functions and when you talk about the tangent plane you are thinking about their graphs.

6. Jul 31, 2011

### HallsofIvy

This same question was asked in "Homework: Caculus and Beyond" so I am combining the two threads. newyorkcity, do NOT post the same question more than once.