Aim: What Happens When We Enlarge Or Decrease The Size Of

An Object?

Do Now

Does a dilations always involve a change in size?

List three examples to support you answers.

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Dilations of everyday occurrences

You are probably familiar with the word "dilate" as it relates to the eye.  The pupil of the eye dilates (gets larger or smaller) depending upon the amount of light striking the eye.

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Definition of a dilation

http://www.amathsdictionaryforkids.com/

http://intermath.coe.uga.edu/dictnary/homepg.asp

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Dilations that occur in transformational geometry

• The description of a dilation includes the scale factor and the center of the dilation.

• A dilation of scalar factor k whose center of dilation is the originmay be written:  Dk(x,y) = (kx,ky).

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Dilations that occur in transformational geometry

If the scale factor is greater than 1, the image is an enlargement.If the scale factor is between 0 and 1, the image is a reduction.

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Student ActivityExploring dilations

Students will complete the handout as they work with interactive website to explore and understand dilations.

http://www.learnalberta.ca/content/mejhm/html/object_interactives/dilatations/use_it.html?launch=true

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Summary

Does location matter when a set of points or an object is dilated in plane?

Aim: What Happens When We Enlarge Or Decrease The Size Of An Object?

Additional ResourcesThe next lesson will have students modeling dilations using Geometer’s Sketchpad.

Homework JMAP HANDOUT

Standards

Standard MST3: Mathematics (1997)

Performance Indicator MST3.C.OP3.MB.C: Students use transformations on figures and functions in the coordinate plane.

Standard MST3: Mathematics (2005)

Performance Indicator MST3.IG.GE8.58:

Students define, investigate, justify, and

apply similarities (dilations and the

composition of dilations and isometries).