Dilation & Rotation Rules

Dilation & Rotation Rules

Learning Target

• I can determine how scale factors dilate figures.

Dilation

• Increase or Decrease in a figure on the coordinate plane.

• Determined by the scale factor given.

• Point P ( 1, 3) is dilated by a scale factor of 3

• What is Point P'?

• P' ( 3, 9)

• Rule: ( 3x, 3y)

Dilation

• Did the figure increase or decrease?

• Point H ( 2, 6)

• Dilated by a scale factor of 1/2.

• What are the coordinates of H'?

• Point H' ( 1, 3)

• Rule:  $\left(\frac{1}{2}x,\ \frac{1}{2}y\right)$  

To Determine

Scale Factor

• Scale Factor can be found by...

•  $\frac{image}{pre-image}$  

• Find the scale factor in the given dilation.

• Point M ( 1, 4) and Point M' ( 2, 8)

•  $\frac{image}{pre-image}=\frac{2}{1}=2$  

• the scale factor is 2: ( 2x, 2y)

Scale Factors

• Scale factor > 1: increase in size

• Scale factor > 1: decrease in size

• Scale factor = 1.........?

Multiple Choice

Point J ( -5, 6) is dilated by a scale factor of 3. What are the coordinates of Point J'?

• ( -15, 6)

• ( -15, 18)

• ( -2, 9)

• ( -5, 18)

Multiple Choice

A figure is dilated by a scale factor of 1, what are the effects?

• The figure increased

• The figure decreased

• The figure stayed the same size

Multiple Choice

Point A is ( 7, 3) and Point A' is ( 21, 9). What is the scale factor for the dilation?

• $\left(\frac{1}{3}x,\ \frac{1}{3}y\right)$

• $\left(x+14,\ y+6\right)$

• $\left(3x,\ 3y\right)$

Small Group this Afternoon