Schema: Read page 39 Do #1-3

1.5 Segment and Angle Measurement

Ruler Postulate The distance between points A and B (written as AB ) is the absolute value of the difference between the coordinates of A and B.

Between When three points lie on a line, one of them is between the other two.

Do # 4

Segment Addition Postulate If B is between A and C, then AB + BC = AC Or If AB + BC = AC, then B is between A and C.

Example Use the diagram to find EF. 16 – 10 = 10 + EF – 10 Subtract 10 from each side. 6 = EF Simplify. 16 = 10 + EF Substitute 16 for DF and 10 for DE. SOLUTION DF = DE + EF Segment Addition Postulate

Do #5

#5

Read page 41 Do #6

Example 1 (p.41)

Example 2 (p42)

Try these A : add to homework

Measuring angles... What tool do we use to measure angles? Protractor What is the unit of measure for angles? Degrees

Protractor Here is a standard protractor like you use in the classroom.

When we use a protractor, we need to line it up correctly. You need to make sure the protractor is lined up correctly. Is this ready to measure the angle?

Were you right it wasn’t Look for the upside down ‘T’ in the middle of the straight line on your protractor. This needs to be exactly on the vertex of your angle.

We need to remember..... It doesn’t matter which way around the angle is, you ALWAYS need to line the upside down ‘T’ to the vertex of the angle.

Now you are ready. Read from the 0°, and follow the inner set of numbers.

Once you reach 30° you need to be careful!!! You then need to look at the 1° markings on the outer set of numbers.

What does the angle measure? This angle measures 35°.

Do #7

Angle Addition Postulate If P is in the interior of, then: S R T P

Congruent Angles = Angles that have the same measure. AP

Example 3 (p44)

Guided Example

Try These B (for HW)

Check Your Understanding (p46) for HW