Abstract Algebra | The dihedral group

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  • čas přidán 14. 01. 2020
  • We present the group of symmetries of a regular n-gon, that is the dihedral group D_n.
    www.michael-penn.net
    www.randolphcollege.edu/mathem...

Komentáře • 28

  • @franciscodanielquiroz9904

    Why nobody is talking about how cool it is that he snaps his fingers to clean the board? As mathematics teacher I create my own videos as well and this gives me great ideas! Love this video.

  • @basakatik4770
    @basakatik4770 Před 3 lety +5

    Finally I got the concept totally! Thank you very much for this clear and wonderful explanation!

  • @cycklist
    @cycklist Před 4 lety +10

    Your channel is so good. It's wonderful to watch this more advanced stuff; it takes me back to my undergraduate days and all those happy memories. Best wishes to you from the UK.

    • @paul21353
      @paul21353 Před 3 lety +1

      This absolutely is the same for me. These video's take me back to my first years studying math at my uni and also it brings the joy of understanding the material better than back in those early years.

  • @liranekm
    @liranekm Před 2 lety +1

    OMG This is gold .
    Love my math instructor but me not taking number theory has been a set back.
    THANK YOU

  • @abnereliberganzahernandez6337

    This Is my Man right there! One of my favorite videos all Time.

  • @user-xm9xo7jg4u
    @user-xm9xo7jg4u Před 3 lety +9

    The previous video is czcams.com/video/rapZj9yqsNw/video.html

  • @user-xm9xo7jg4u
    @user-xm9xo7jg4u Před 3 lety

    Love your channel so much. Thanks for sharing.

  • @eduardohenriquerodriguesdo6103

    another proof of rs=sr^(n-1):
    note that they are inverses. Because they are both reflections,it must be the case that they are equal.

  • @paul21353
    @paul21353 Před 3 lety +3

    The drawings starting around 7:50, combining rotation and reflexion of an n-gon presuppose that n is odd. Strictly speaking you should check that the result is the same when n is even.

  • @lancelofjohn6995
    @lancelofjohn6995 Před 3 lety +1

    nice,in the end the r^(k+1)=s*r^n*r^n-(k+1)

  • @georgettebeulah4427
    @georgettebeulah4427 Před 4 lety +4

    I love this explanation I can relate with it a lot thank you for loading on time

  • @SanketAlekar
    @SanketAlekar Před 2 lety

    At 10:00, it should be n-1 clockwise rotations (r^n-1) followed by a reflection that fixes 1 (s) to be consistent. What you did was n-1 counter-clockwise rotations (r^(n-1))^(n-1), following by a reflection that fixes n (which is not s).

  • @muhammadfarooq2486
    @muhammadfarooq2486 Před 3 lety

    Best explanation

  • @joetursi9573
    @joetursi9573 Před 2 lety

    We must be careful not to confuse rotation as being restricted to it's common definition of rotating through 2pi or 360 degrees. In this context a rotation means a "motion." If not then writing that the number of rotations=2(pi) K/n where k is )=k-< or equal to n-1 is confusing. Example: Set n=3 (a triangle) we have that 2(pi) k/3- the number of rotations, implying K=9/2(pi) which is about 3/2( not even an integer in the set[0,N-1} . It's about one and a half rotations which certainly note equal to what is correct:3 .

  • @user-td6pl6wk6s
    @user-td6pl6wk6s Před 2 lety

    Great

  • @sudhansh6998
    @sudhansh6998 Před 4 lety

    Just a small nitpick, but I think you forgot to include closure in your definition of a group

    • @iamtackler
      @iamtackler Před 3 lety +3

      * being a binary operation requires closure under * by definition

  • @MathematicalMinds
    @MathematicalMinds Před rokem

    Plz define dicyclic group in soft manners

  • @williamsimpson4670
    @williamsimpson4670 Před 4 lety

    17:10 Check the last line of the proof, guys.

    • @rslitman
      @rslitman Před 2 lety

      Yes, I caught that error.

  • @bongo50_
    @bongo50_ Před 2 lety

    Aren’t there 4 axioms of groups? You seem to miss closure.

    • @yarno8086
      @yarno8086 Před rokem +1

      A group is a set combined with a binary operation, meaning the operation is already closure

  • @sapito169
    @sapito169 Před 2 lety +1

    why Quentin Tarantino is making math videos?