geometry chapter 7

cross products

in the proportion a/b=c/d, where b isn’t 0 and d isn’t 0, the cross products are ad and bc. the portion is true if and only if the cross products are equal

dilation

a transformation that enlarges or reduces the original figure proportionally

enlargement

an image that is larger that the original figure

extremes

in a/b=c/d, the numbers a and d

means

in a/b=c/d, the numbers b and c

mid-segment of a triangle

a segment exactly halfway between the endpoints of the segment

proportion

an equation of the form a/b+c/d that states that two ratios are equal

ratio

a comparison of two quantities using division

reduction

an image that is smaller than the original figure

scale factor

the ratio of the lengths of to corresponding sides of two similar polygons or two similar solids

scale

ratio of corresponding lengths between two similar figures, determining how much an object is enlarged or reduced

scale drawing

a two-dimensional representation of an object or place that maintains the same shape as the original, but in a different size

scale model

a miniature representation of a real-world object

similar polygons

geometric figures with the same shape but not necessarily the same size

similarity transformation

a sequence of one or more rigid motions (translations, reflections, or rotations) followed by a dilation