Study Guide 7.1-7.3

7.1   Ratio and Proportion

-A ratio is a comparison of a number a and a nonzero number b using division .
              -Ratios can be written in 3 way . (a to b ... a/b ... a:b)
-A proportion is an equation that states that two ratios are equal.
             

The numbers b and c are the means , and the numbers a and d are the extremes of the proportion .

Cross Product Property - In a proportion ,the product or the extremes is equal to the product of the means .  (a x d =c x d)

7.2    Similar Polygons

In geometry ,two figures that have the same shape are called similar .

Two polygons are SIMILAR POLYGONS if the corresponding angles are congruent and corresponding side lengths are proportional .

 If two polygons are similar ,then the ratio of the lengths of two corresponding sides is called the SCALE FACTOR.

Perimeters of Similar Polygons
     - If two polygons are similar ,then the ratio of their perimeters is equal to the ratio of their corresponding side lengths .

7.3 Showing Triangles Are Similar : AA

Angle -Angle Similarity Postulate (AA)
- If two angles of one triangle are congruent to two angles of another triangle ,then the two triangles are similar .