Geometry warm-up Get a strip of paper from the back

desk. Fold it in half, then half again. Draw a SpongeBob character in the

first frame. Reflect it into the second frame. Reflect that one into the 3rd frame. Then,…. guess what?... Yep. Reflect

that one into the 4th frame.

On a small piece of paper,write your name, then tell me

the effect of a double reflection.Do not discuss this with anyone.

Turn it in.

Let’s grade your homework

Motion in geometry packet.

Motion in the Coordinate Plane

Last time we talked about 3 rigid transformations.

Translation …..

Slides

Rotation …..

Turns

Reflection …..

Flips

Today…

♥ We’re going to talk about those same rigid transformations in the coordinate plane. This is called ...

Wait for it…..

♥ Whatever transformation occurred:♥ moved the x-coordinate 2 units to the right (positive)♥ and the y-coordinate 4 units up (positive).

♥ (reminder) Whatever transformation occurred:♥ moved the x-coordinate 2 units to the right (positive)♥ and the y-coordinate 4 units up (positive).

♥ THIS SAME OPERATION HAPPENS ON EACH POINT. The result is an image that is congruent to the pre-image.

♥ In our Geometry notation, we can write:♥ T(x,y) = (x + 2, y + 4)♥ Read, “the transformation of a point (x,y) moved

right 2 and up 4”

Activities

Volunteers hand out

♥Graph paper

♥Straight edges

“What you should have learned”(write these down in your notebook)

♥ Translations ADD ♥ the same number (positive or negative) to

each of the x-coordinates ♥ and the same number (could be different

from the x-axis addend) to each y-coordinate.♥ The image is congruent to the pre-image

• Reflections –

♥ MULTIPLY the x-coordinate by -1 to reflect across the y-axis

♥ MULTIPLY the y-coordinate by -1 to reflect across the x-axis

for a special reflection:MULTIPLY both coordinates by -1 to end up with a

double reflection: across one axis and then the other.

This is also considered a ROTATION of 180°

You should have learned this, too

(write these down in your notebook)

Rotations

♥ MULTIPLY each coordinate by -1 to rotate a figure 180° about the origin.

♥ Since rotations are based on degrees, there is no ‘rule’ regarding operations on a point.

Let’s Play

Interactive Transformations in the Coordinate Plane

Assignment

♥ 16-3 Packet