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Image of a function

  • Thread starter Frillth
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  • #1
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Homework Statement



I have the function g(s,t) = [(st+1)/(st-1),(s-t)/(st-1),(s+t)/(st-1)], and I need to find its image.

Homework Equations



I know that every point on the image of g lies on the hyperboloid x^2 + y^2 - z^2 = 1.

The Attempt at a Solution



I am very inexperienced with linear algebra, and I need to solve this problem for tomorrow. The problem is, I don't even really understand exactly what an image is. I read that it is like the function's range, but I don't even really know how to define the range of a function in 3D. Could someone please walk me through the steps for how to solve this problem?
 

Answers and Replies

  • #2
HallsofIvy
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I don't know that this really has anything to do with linear algebra. It's really a problem in vector valued functions. You should have learned, back in basic algebra, that the "image" of the function y= f(x) is the set f all possible y values. Here, "y" is a point in 3 dimensions. A good way to start is to write
x= (st+1)/(st-1),
y= (s-t)/(st-1),
z= (s+t)/(st-1).

Now, what are the possible values of x, y, and z? For example, since s and t can be any numbers, st can be any number. If x= (a+1)/(a-1), what are the possible values of x? You might try graphing y= (x+1)/(x-1) to answer that question.
 

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