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Discover the beauty of symmetry through snowflakes, starfish, and more. Learn about reflection, rotation, and translation symmetries. Unleash your creativity by combining symmetries for new patterns in art, music, and dance. Join Chris in a fun dance with friends exploring symmetrical moves within a square. Explore the algebra of symmetries through dance sequences. Find symmetry in knitting, bell ringing, and beyond. Have fun identifying symmetrical patterns in various activities!
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Dancing with maths Chris Budd
What have the following got in common?
They all have symmetry Symmetry is the basis of all patterns In art, music, bell ringing, knitting, dancing, crystals, elementaryparticles and nature
Some types of symmetry Reflexion Rotation Translation
Something is symmetric if it is not changed by one of these operations Lots of good artistic patterns have this property
A square is very symmetric … how Many symmetries does it have?
8 4Rotation symmetries 4Reflexion symmetries
a Rotation Reflexion b Reflexion c
Simplest symmetry .. Do nothing Call this symmetry e
Can combine symmetries to get new ones a rotation of 90 degrees aa rotation of 180 degrees aaa rotation of 270 degrees aaaa rotation of 360 degrees e aaaa =
Can combine reflexions with themselves bb = ecc = edd = eff = e What happens if we combine a reflexion with a rotation? or two different reflexions?
Reflexion and rotation = ba = ? ba = c Reflexion and rotation = reflexion
So … what is ab ab = d
Now combine two reflexions bc = ? Remember This!!!!! bc = a
Some other combinations cb = aaa db = abb = ae= a
Let’s start dancing! My name is Chris. I go to a dance with my friends Andrew, Bryony and Daphne A B C D
We make ABCD four corners of a square Key Fact The symmetries of the square correspond to different dance moves
Symmetry: b Reflexion Dance move: b A B C D A C B D An inner-twiddle or dos-e-dos
Symmetry: c Reflexion Dance move: c A B C D B A D C An outer-twiddle or swing
Now for the clever bit! In the algebra of symmetries Did you remember this? bc = a Therefore bcbcbcbc = aaaa = e
So what????? This corresponds to a dance called a Reel of Four or a Hey Let’s do the dance
ABCD ACBD CADB CDAB DCBA DBCA BDAC BADC ABCD b c b c b c b c
Another dance d ABCD CDAB d b = a dbdbdbdb = aaaa = e
ABCD CDAB CADB DBCA DCBA BADC BDAC ACBD ABCD d b d b d b d b
We see the same patterns in knitting and in bell ringing And many other places How many can you find?