Geometry Notes

Section 1-2

9/6/07

What you’ll learn

How to measure segments and determine accuracy of measurements

How to identify and model line segments How to compute with measures

Vocabulary Terms:

Line segment Precision Betweeness of points Between Congruent

Line Segment—a section of a line from one endpoint to another endpoint Draw it with 2 dots (one at

each end) and a straight line between them

Name it with by the endpts

Fact: the measure of a segment is written by naming the endpts with capitol printed letters

Words/Symbols:Words/Symbols: PQPQ

P

Q

Between

There are infinitely many points between the endpoints of a line segment

Congruent Segments

Congruent figures have the same size and shape

Since all segments have the same shape we only need to verify that two segments have the same measure to be congruent

Precision

Not all measurements are the same– some are more precise than others.

How can you tell? Is there a method to determine the precision/accuracy of your measurement?

Why yes. . . There is. . .

How to determine precision First you must determine the smallest unit

of measure used. Are they counting by ones? Halves? Quarters?

Measurements are good to about one half of the smallest unit used so cut that number in half.

This will tell you how far over or under your measurement might be. For over, add it to the original measurement; for under, subtract it from the original measurement.

Example: the measurement is 10in Determine the smallest unit of measure

used. Are they counting by ones? Halves? Quarters?

Measurements are good to about one half of the smallest unit used so cut that number in half.

They are counting by ones

Half of one is ½

10+ ½=10½ ; 10 - ½ =9½

So we might be ½ over or ½ under. For over, add it; for under, subtract it.

Example: measurement 5½ in Determine the smallest unit of measure

used. Are they counting by ones? Halves? Quarters?

Measurements are good to about one half of the smallest unit used so cut that number in half.

So we might be ¼ over or ¼ under. For over, add it; for under, subtract it.

They are counting by halves

Half of ½ is ¼

5½ + ¼ = 5¾ ; 5½ - ¼ = 5¼

Have you learned

How to measure segments and determine accuracy of measurements?

How to identify and model line segments? How to compute with measures? Your assignment is

P. 17 (13-45 odd, 57-65odd) & Notes 1-3