Proof of Cauchy-Schwarz Inequality

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SUMMARY

The discussion centers on proving the Cauchy-Schwarz inequality, specifically through the use of inner products of vectors. The participant initially attempted an induction approach but encountered complications during summation. A professor's hint suggested leveraging the relationship between geometric and arithmetic means, yet the participant struggled to progress. The recommended method involves examining the inner product of the expression x + a*y, where x and y are vectors and a is a scalar, ensuring positivity for all values of a to derive the inequality.

PREREQUISITES
  • Understanding of vector inner products
  • Familiarity with the Cauchy-Schwarz inequality
  • Basic knowledge of arithmetic and geometric means
  • Experience with mathematical induction
NEXT STEPS
  • Study the proof of the Cauchy-Schwarz inequality using inner products
  • Explore the relationship between arithmetic and geometric means
  • Review mathematical induction techniques in proofs
  • Investigate applications of the Cauchy-Schwarz inequality in various mathematical fields
USEFUL FOR

Students studying mathematics, particularly those focused on linear algebra and inequalities, as well as educators seeking effective proof strategies for the Cauchy-Schwarz inequality.

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I have a homework problem in which I have to prove the Cauchy-Schwarz inequality. I tried to do it by induction, but when I try to do summation to 2, I get a mess of terms. The professor hinted that one can use the fact that geometric means are less than or equal the arithmetic mean, but I can't seem get past just that hint. Should I continue trying induction or am going down the wrong road?
 
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The slick way is to look at the inner product of x+a*y with itself, where x,y are vectors and a is a scalar. This must be positive for all a, and picking the right a will give you the result.
 

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