Abstract Algebra | The dihedral group

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  • Опубліковано 14 січ 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...

КОМЕНТАРІ • 28

  • @franciscodanielquiroz9904
    @franciscodanielquiroz9904 3 роки тому +7

    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 3 роки тому +5

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

  • @user-xm9xo7jg4u
    @user-xm9xo7jg4u 3 роки тому +9

    The previous video is ua-cam.com/video/rapZj9yqsNw/v-deo.html

  • @liranekm
    @liranekm 2 роки тому +1

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

  • @cycklist
    @cycklist 4 роки тому +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 3 роки тому +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.

  • @abnereliberganzahernandez6337

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

  • @paul21353
    @paul21353 3 роки тому +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.

  • @user-xm9xo7jg4u
    @user-xm9xo7jg4u 3 роки тому

    Love your channel so much. Thanks for sharing.

  • @eduardohenriquerodriguesdo6103
    @eduardohenriquerodriguesdo6103 4 роки тому +18

    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.

  • @lancelofjohn6995
    @lancelofjohn6995 3 роки тому +1

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

  • @georgettebeulah4427
    @georgettebeulah4427 4 роки тому +4

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

  • @SanketAlekar
    @SanketAlekar 2 роки тому

    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 3 роки тому

    Best explanation

  • @joetursi9573
    @joetursi9573 2 роки тому

    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 2 роки тому

    Great

  • @MathematicalMinds
    @MathematicalMinds Рік тому

    Plz define dicyclic group in soft manners

  • @sapito169
    @sapito169 2 роки тому +1

    why Quentin Tarantino is making math videos?

  • @sudhansh6998
    @sudhansh6998 3 роки тому

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

    • @iamtackler
      @iamtackler 3 роки тому +3

      * being a binary operation requires closure under * by definition

  • @bongo50_
    @bongo50_ 2 роки тому

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

    • @yarno8086
      @yarno8086 Рік тому +1

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

  • @williamsimpson4670
    @williamsimpson4670 4 роки тому

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

    • @rslitman
      @rslitman 2 роки тому

      Yes, I caught that error.