Math 5270 Transformational Geometryemina/teaching/5270s13/5270_Day5_notes.pdf · Day 5, Summer 13...

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Math 5270 Transformational Geometry Day 5 Summer 13 Day 5, Summer 13 Math 5270 Transformational Geometry 1/19

Transcript of Math 5270 Transformational Geometryemina/teaching/5270s13/5270_Day5_notes.pdf · Day 5, Summer 13...

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Math 5270Transformational Geometry

Day 5

Summer 13

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Composition of rotations

Composing rotations about the same point yields a rotation.

Such rotations commute.

Composing rotations about different points yield a rotation...

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Composition of rotations

Composing rotations about the same point yields a rotation.

Such rotations commute.

Composing rotations about different points yield a rotation...

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Use your geogebra to

Make an angle slider for angle α between 0◦ and 360◦

In input bar write β = 360◦ − α

Pick any two points A and B and observe the composition of

rotation about A by α, followed by rotation about B by β.

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Group of rotations R?

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Equation for the rotation not around the origin?

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Alternative?

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How can we tell two isometries are the same?

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Reflections

Definition

wthout coordinates

with coordinates

Hmm... I think I might need more space...

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Reflections

Definition

wthout coordinates

with coordinates

Hmm... I think I might need more space...

Day 5, Summer 13 Math 5270 Transformational Geometry 8/19

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Equation for a reflection

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Equation for a reflection, take 2

Any super easy reflections you know?

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Fixed points, fixed sets?

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What happens when you compose two reflections?

Use your geogebra to observe what happens when you compose

different reflections.

Why did I say different?

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Group of reflections?

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Every isometry is a composition of reflections!

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Some of students’ work

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Congruence...

CCSS.Math.Content.HSG-CO.B.7 Use the definition of

congruence in terms of rigid motions to show that two

triangles are congruent if and only if corresponding pairs of

sides and corresponding pairs of angles are congruent.

CCSS.Math.Content.HSG-CO.B.8 Explain how the criteria for

triangle congruence (ASA, SAS, and SSS) follow from the

definition of congruence in terms of rigid motions.

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Congruence...

CCSS.Math.Content.HSG-CO.B.7 Use the definition of

congruence in terms of rigid motions to show that two

triangles are congruent if and only if corresponding pairs of

sides and corresponding pairs of angles are congruent.

CCSS.Math.Content.HSG-CO.B.8 Explain how the criteria for

triangle congruence (ASA, SAS, and SSS) follow from the

definition of congruence in terms of rigid motions.

Day 5, Summer 13 Math 5270 Transformational Geometry 18/19

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