Minimizing Distance Between Two Lines

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SUMMARY

The discussion focuses on minimizing the distance between two lines, L1 and L2, defined by their directional vectors a1 and a2, respectively. The objective is to find the closest points x1a1 on L1 and b + x2a2 on L2 by minimizing the expression ||x1a1 - x2a2 - b||. The user initially struggled with the correct equations but ultimately clarified their understanding of the problem, particularly regarding the use of derivatives and projections in vector calculus.

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  • Understanding of vector calculus and derivatives
  • Familiarity with the concepts of line equations in vector form
  • Knowledge of projections in linear algebra
  • Basic proficiency in optimization techniques
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  • Study vector projection techniques in linear algebra
  • Learn about optimization methods in calculus
  • Explore the derivation of distance minimization equations for lines
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Mathematicians, engineers, and computer scientists interested in optimization problems, particularly those involving geometric interpretations of vectors and lines.

bodensee9
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Can someone help with the folowing?
Suppose L1 is the line through the origin in the direction of a1 and L2 is the line through b in the direction of a2. I am supposed to find the closest points x1a1 and b+x2a2 on the two lines.

So I am trying to find the equations that would minize ||x1a1-x2a2-b||.

Not really sure what equations to write. I know that I'm trying to find some vector c so that (c-x1a1+x2a2+b)^2 will be the minimum. This means that if I take the derivative of the above, then the derivative will be zero. So, if I break c down into its components, would I get

2(c1-x1a1)+2(c2+x2a2+b)=0? Or, would I be trying to find the projection of x2a2+b onto a1? And if I do that, would be projection from a2 onto a1 be a1(a1Ta1)-1aT? But what about for a2? Not sure if that's right either. Thanks.
 
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Figured out. misunderstood the problem at first. thanks.
 

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