How Do General Plane Equations Differ from Tangent Surface Equations?

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The general plane equation, a(x - x_0) + b(y - y_0) + c(z - z_0) = 0, represents any plane in three-dimensional space, defined by a normal vector (a, b, c). In contrast, the tangent surface equation, z - z_0 = f_x(x_0, y_0)(x - x_0) + f_y(x_0, y_0)(y - y_0), describes a plane that is tangent to a surface at a specific point, with its normal vector derived from the surface's partial derivatives. Both equations describe planes but serve different purposes in geometry and calculus. The first is more general, while the second is specific to tangent planes. Understanding this distinction is crucial for applications in multivariable calculus.
Calpalned
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Homework Statement


What's the difference between the two equations for a plane?

This question is somewhat related to my other, overarching question here: https://www.physicsforums.com/threads/i-am-confused-about-how-multivariable-calc-works.798798/

Homework Equations


## a(x - x_0) + b(y - y_0) + c(z - z_0) = 0 ##
and
## z - z_0 = f_x (x_0, y_0)(x-x_0) + f_y (x_0, y_0)(y-y_0) ##

The Attempt at a Solution


I'm not sure what the relationship between these two equations are. Thanks everyone.
 
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Calpalned said:

Homework Statement


What's the difference between the two equations for a plane?

Homework Equations


## a(x - x_0) + b(y - y_0) + c(z - z_0) = 0 ##
and
## z - z_0 = f_x (x_0, y_0)(x-x_0) + f_y (x_0, y_0)(y-y_0) ##

The Attempt at a Solution


I'm not sure what the relationship between these two equations are. Thanks everyone.

There's no deep difference. The first is the general form of a plane with ##(a,b,c)## as a normal vector. The second is a specific example of a plane corresponding to a tangent surface with normal vector ##(f_x,f_y,-1)##.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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