Author:
Todd Parks

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Tutorial

**Student Outcomes**

1. Students describe the effect of dilations on two-dimensional figures using coordinates (Lesson 6).

2. Students know an informal proof of why dilations are degree-preserving transformations and map segments to segments, lines to lines, and rays to rays.

**Lesson Review**

-We know that we can calculate the coordinates of a dilated point given the coordinates of the original point and the scale factor.

-To find the coordinates of a dilated point we must multiply both the -coordinate and the -coordinate by the scale factor of dilation.

-If we know how to find the coordinates of a dilated point, we can find the location of a dilated triangle or other two dimensional figure.

**Lesson Summary**

- Dilation has a multiplicative effect on the coordinates of a point in the plane. Given a point in the plane, a dilation from the origin with scale factor moves the point to
- For example, if a point in the plane is dilated from the origin by a scale factor of , then the coordinates of the dilated point are

Remember: In order to dilate an object and make it **bigger**, you need to *multiply by a scale factor *that is __greater than 1.__

In order to dilate an object and make it **smaller**, you need to *multiply by a scale factor* that is a fraction __greater than 0 but less than 1.__