# 1-3 Measuring and Constructing Segments Holt Geometry Warm Up Warm Up Lesson Presentation Lesson Presentation Lesson Quiz Lesson Quiz

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1-3 Measuring and Constructing Segments Holt Geometry Warm Up Warm Up Lesson Presentation Lesson Presentation Lesson Quiz Lesson Quiz Slide 2 Warm Up Simplify. 1. 7 (3) 2. 1 (13) 3. |7 1| Solve each equation. 4. 2x + 3 = 9x 115. 3x = 4x 5 6. How many numbers are there between and ? 10 12 8 25 Infinitely many 1-3 Segments and Their Measures Slide 3 Use length and midpoint of a segment. Construct midpoints and congruent segments. Objectives 1-3 Segments and Their Measures Slide 4 coordinatemidpoint distancebisect lengthsegment bisector ConstructionDistance Formula BetweenPostulates congruent segments Vocabulary 1-3 Segments and Their Measures Slide 5 A ruler can be used to measure the distance between two points. A point corresponds to one and only one number on a ruler. The number is called a coordinate. The following postulate summarizes this concept. 1-3 Segments and Their Measures Slide 6 Slide 7 AB = |a b| or |b - a| A a B b The distance between any two points is the absolute value of the difference of the coordinates. If the coordinates of points A and B are a and b, then the distance between A and B is |a b| or |b a|. The distance between A and B is also called the length of AB, or AB. 1-3 Segments and Their Measures Slide 8 Example 1: Finding the Length of a Segment Find each length. = 2 A. BCB. AC = |1 3| BC = |1 3| = 5 = | 5| AC = |2 3| 1-3 Segments and Their Measures Slide 9 Find each length. Check It Out! Example 1 a. XY b. XZ 1-3 Segments and Their Measures Slide 10 Congruent segments are segments that have the same length. In the diagram, PQ = RS, so you can write PQ RS. This is read as segment PQ is congruent to segment RS. Tick marks are used in a figure to show congruent segments. 1-3 Segments and Their Measures Slide 11 You can make a sketch or measure and draw a segment. These may not be exact. A construction is a way of creating a figure that is more precise. One way to make a geometric construction is to use a compass and straightedge. 1-3 Segments and Their Measures Slide 12 Example 2: Copying a Segment Sketch, draw, and construct a segment congruent to MN. Step 1 Estimate and sketch. Estimate the length of MN and sketch PQ approximately the same length. PQ 1-3 Segments and Their Measures Slide 13 Example 2 Continued Sketch, draw, and construct a segment congruent to MN. Step 2 Measure and draw. Use a ruler to measure MN. MN appears to be 3.5 in. Use a ruler to draw XY to have length 3.5 in. XY 1-3 Segments and Their Measures Slide 14 Example 2 Continued Sketch, draw, and construct a segment congruent to MN. Step 3 Construct and compare. Use a compass and straightedge to construct ST congruent to MN. A ruler shows that PQ and XY are approximately the same length as MN, but ST is precisely the same length. 1-3 Segments and Their Measures Slide 15 Check It Out! Example 2 Sketch, draw, and construct a segment congruent to JK. Step 1 Estimate and sketch. Estimate the length of JK and sketch PQ approximately the same length. 1-3 Segments and Their Measures Slide 16 Check It Out! Example 2 Continued Step 2 Measure and draw. Use a ruler to measure JK. JK appears to be 1.7 in. Use a ruler to draw XY to have length 1.7 in. Sketch, draw, and construct a segment congruent to JK. 1-3 Segments and Their Measures Slide 17 Step 3 Construct and compare. Use a compass and straightedge to construct ST congruent to JK. A ruler shows that PQ and XY are approximately the same length as JK, but ST is precisely the same length. Check It Out! Example 2 Continued Sketch, draw, and construct a segment congruent to JK. 1-3 Segments and Their Measures Slide 18 In order for you to say that a point B is between two points A and C, all three points must lie on the same line, and AB + BC = AC. 1-3 Segments and Their Measures Slide 19 Example 3A: Using the Segment Addition Postulate G is between F and H, FG = 6, and FH = 11. Find GH. 5 = GH FH = FG + GH Seg. Add. Postulate 11 = 6 + GH 6 6 Substitute 6 for FG and 11 for FH. Subtract 6 from both sides. Simplify. 1-3 Segments and Their Measures Slide 20 Example 3B: Using the Segment Addition Postulate M is between N and O. Find NO. 10 = 2x NM + MO = NO Seg. Add. Postulate 17 + (3x 5) = 5x + 2 2 2 Substitute the given values Subtract 2 from both sides. Simplify. 3x + 12 = 5x + 2 3x + 10 = 5x 3x 3x 2 2 5 = x Simplify. Subtract 3x from both sides. Divide both sides by 2. 1-3 Segments and Their Measures Slide 21 Example 3B Continued M is between N and O. Find NO. NO = 5x + 2 Substitute 5 for x. Simplify. = 27 = 5(5) + 2 1-3 Segments and Their Measures Slide 22 Check It Out! Example 3a Y is between X and Z, XZ = 3, and XY =. Find YZ. XZ = XY + YZ Seg. Add. Postulate Substitute the given values. Subtract from both sides. 1-3 Segments and Their Measures Slide 23 E is between D and F. Find DF. Check It Out! Example 3b DE + EF = DF Seg. Add. Postulate (3x 1) + 13 = 6x 3x Substitute the given values Subtract 3x from both sides. 3x + 12 = 6x 12 = 3x 4 = x Simplify. Divide both sides by 3. 12 3x 3 3 = 1-3 Segments and Their Measures Slide 24 E is between D and F. Find DF. Check It Out! Example 3b Continued DF = 6x Substitute 4 for x. Simplify. = 24 = 6(4) 1-3 Segments and Their Measures Slide 25 The midpoint M of AB is the point that bisects, or divides, the segment into two congruent segments. If M is the midpoint of AB, then AM = MB. So if AB = 6, then AM = 3 and MB = 3. 1-3 Segments and Their Measures Slide 26 Example 4: Recreation Application The map shows the route for a race. You are at X, 6000 ft from the first checkpoint C. The second checkpoint D is located at the midpoint between C and the end of the race Y. The total race is 3 miles. How far apart are the 2 checkpoints? XY = 3(5280 ft) Convert race distance to feet. = 15,840 ft 1-3 Segments and Their Measures Slide 27 Example 4 Continued XC + CY = XY Seg. Add. Post. 6000 + CY = 15,840 Substitute 6000 for XC and 15,840 for XY. 6000 Subtract 6000 from both sides. Simplify. CY = 9840 = 4920 ft The checkpoints are 4920 ft apart. D is the mdpt. of CY, so CD = CY. 1-3 Segments and Their Measures Slide 28 Check It Out! Example 4 You are 1182.5 m from the first-aid station. What is the distance to a drink station located at the midpoint between your current location and the first-aid station? The distance XY is 1182.5 m. The midpoint would be. 1-3 Segments and Their Measures Slide 29 Example 5: Using Midpoints to Find Lengths D F E 4x + 6 7x 9 4x + 6 = 7x 9 6 = 3x 9 15 = 3x Step 1 Solve for x. ED = DF 4x +9 + 9 Substitute 4x + 6 for ED and 7x 9 for DF. D is the mdpt. of EF. Subtract 4x from both sides. Simplify. Add 9 to both sides. Simplify. D is the midpoint of EF, ED = 4x + 6, and DF = 7x 9. Find ED, DF, and EF. 1-3 Segments and Their Measures Slide 30 Example 5 Continued D F E 4x + 6 7x 9 x = 5 3 15 3x = Divide both sides by 3. Simplify. D is the midpoint of EF, ED = 4x + 6, and DF = 7x 9. Find ED, DF, and EF. 1-3 Segments and Their Measures Slide 31 Example 5 Continued D F E 4x + 6 7x 9 ED = 4x + 6 = 4(5) + 6 = 26 DF = 7x 9 = 7(5) 9 = 26 EF = ED + DF = 26 + 26 = 52 Step 2 Find ED, DF, and EF. D is the midpoint of EF, ED = 4x + 6, and DF = 7x 9. Find ED, DF, and EF. 1-3 Segments and Their Measures Slide 32 Check It Out! Example 5 S is the midpoint of RT, RS = 2x, and ST = 3x 2. Find RS, ST, and RT. ST R 2x3x 2 2x = 3x 2 x = 2 Step 1 Solve for x. RS = ST +3x Substitute 2x for RS and 3x 2 for ST. S is the mdpt. of RT. Add 3x to both sides. Simplify. 1-3 Segments and Their Measures Slide 33 Check It Out! Example 5 Continued S is the midpoint of RT, RS = 2x, and ST = 3x 2. Find RS, ST, and RT. ST R 2x3x 2 RS = 2x = 2(2) = 4 ST = 3x 2 = 3(2) 2 = 4 RT = RS + ST = 4 + 4 = 8 Step 2 Find RS, ST, and RT. 1-3 Segments and Their Measures Slide 34 Example 6: Using Distance Formula 1-3 Segments and Their Measures Slide 35 Example 6 Continued 1-3 Segments and Their Measures 1.Find the lengths of the segments. 2.Tell whether any of the segments have the same length. Slide 36 Example 6 Continued 1-3 Segments and Their Measures Slide 37 Example 7: Pythagorean Theorem 1-3 Segments and Their Measures Slide 38 Example 7 Continued 1-3 Segments and Their Measures Slide 39 Example 7 Continued 1-3 Segments and Their Measures Slide 40 Example 7 Continued 1-3 Segments and Their Measures Slide 41 Lesson Quiz: Part I 1. M is between N and O. MO = 15, and MN = 7.6. Find NO. 22.6 2. S is the midpoint of TV, TS = 4x 7, and SV = 5x 15. Find TS, SV, and TV. 25, 25, 50 3. Sketch, draw, and construct a segment congruent to CD. Check students' constructions 1-3 Segments and Their Measures Slide 42 4. LH bisects GK at M. GM = 2x + 6, and GK = 24. Find x. Lesson Quiz: Part II 3 5.Tell whether the statement below is sometimes, always, or never true. Support your answer with a sketch. If M is the midpoint of KL, then M, K, and L are collinear. K L M Always 1-3 Segments and Their Measures Slide 43 6. Use the distance formula to decide if any segment is congruent. P(-1, -6) Q(-8, 5) R(3, -2) Lesson Quiz: Part II 1-3 Segments and Their Measures Thus PQ and RQ are congruent. Slide 44 1-1 Patterns and Inductive Reasoning Skills Autonomous Practice Pages: 21, 22, 23, 24

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