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Identify intersections of lines and planes, apply ruler and segment addition postulates, and solve distance problems using coordinates and absolute values in this geometry review.
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WARM UP 1.5 • On desk!
Use the diagram at the right. 1. Name the intersection of BE and CD. point D ANSWER 2. Name the intersection of BEand plane A. point B ANSWER 3. Name the intersection of DBand planeF. Point E ANSWER REVIEW Daily Quiz 1.4
Use the diagram at the right. 4. Name the intersection of planes AandF. 5. Sketch two lines that intersect a plane at the same point. ANSWER Sample answer: The planes do not appear to intersect. ANSWER
ESSENTIAL OBJECTIVE: How do we apply the ruler postulate and the segment addition postulate? 1.5
VOCABULARY • The real number that corresponds to a point is the coordinate of a point. • The distance between points A and B, written AB, is the absolute value of the difference of the coordinates of A and B.
VOCABULARY • The real number that corresponds to a point is the coordinate of a point. • The distance between points A and B, written AB, is the absolute value of the difference of the coordinates of A and B. • AB is also called the length of AB .
VOCABULARY Segments that have the same length are called congruent segments.
Segment Addition Postulate • If B is between A and C, then AC= AB +BC. • If AC =AB +BC, then B is between A and C.
Segment Addition Postulate • If B is between A and C, then AC= AB +BC. • If AC =AB +BC, then B is between A and C.
Segment Addition Postulate If B is between A and C, then AC= AB +BC. If AC =AB +BC, then B is between A and C.
Segment Addition Postulate If B is between A and C, then AC= AB +BC. If AC =AB +BC, then B is between A and C.
Example 2 SOLUTION Because the three cities lie on a line, you can use the Segment Addition Postulate. Find a Distance by Adding Use the map to find the distance from Athens to Albany. AB = AM + MB = 80 + 90 = 170 The distance from Athens to Albany is 170 miles. ANSWER
Example 3 Find a Distance by Subtracting Use the diagram to find EF. SOLUTION DF = DE + EF Segment Addition Postulate 16=10 + EF Substitute 16 for DFand 10 for DE. 16 – 10=10 + EF – 10 Subtract 10 from each side. 6 = EF Simplify.
Checkpoint Use the Segment Addition Postulate Find the length. 3. Find AC. 4. Find ST.
More……… Use the Segment Addition Postulate Find the length. 3. Find AC. 20 ANSWER 4. Find ST. 8 ANSWER
Example 4 SOLUTION For a horizontal segment, DE = 1 – (–3) = 4 = 4 For a vertical segment, FG = –3–1 = –4 = 4 COORDINATE PLANE: Absolute Value Sign Are the segments shown in the coordinate plane congruent? DE and FG have the same length. So,DEFG. ANSWER
GIZMOS: Distance in the X-Y Plane
Exit Ticket Plot the points in a coordinate plane. Then decide whether AB and CD are congruent. Use Graphing Paper and plot the points. 1. A(–2, 3),B(3, 3),C(–3, 4),D(–3, –1) 2. A(0, 5),B(0, –1),C(5, 0),D(–1, 0) GRAPHING PAPER!
Exit Ticket Plot the points in a coordinate plane. Then decide whether AB and CD are congruent. ANSWER yes; ANSWER yes; Use Graphing Boards and plot the points. 1. A(–2, 3),B(3, 3),C(–3, 4),D(–3, –1) 2. A(0, 5),B(0, –1),C(5, 0),D(–1, 0)
Daily Quiz HwWorksheet 1.5 B