1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Help with Determinants

  1. Oct 22, 2007 #1
    1. The proof that det(kA) = k^ndetA where A is nxn
    I read somewhere that det(rI(n)) = r^(n)
    so det(rA) = det(rI(n).A) = r^ndetA but I am really confused about how they got that? Is I the identity matrix? What would the det(I) be?
  2. jcsd
  3. Oct 22, 2007 #2


    User Avatar
    Homework Helper
    Gold Member

    You pretty much got it.

    We know that det(AB) = det(A)det(B).


    det(rA) = det(rI[n]A) = det(rI[n])det(A) = r^n det(I[n]) det(A) = r^n (1) det(A) = r^n det(A)

    I showed every step possible basically.

    Yes, the determinant of I[n] is always 1. It is the identity matrix.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Help with Determinants
  1. Determinate proof help (Replies: 6)