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Skateboard. In the skateboard design, VW bisects XY at point T , and XT = 39.9 cm . Find XY. Point T is the midpoint of XY . So , XT = TY = 39.9 cm. EXAMPLE 1. Find segment lengths. SOLUTION. XY = XT + TY. Segment Addition Postulate. = 39.9 + 39.9. Substitute. = 79.8 cm.
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Skateboard In the skateboard design, VWbisects XYat point T, and XT=39.9cm. Find XY. Point Tis the midpoint of XY . So, XT = TY = 39.9cm. EXAMPLE 1 Find segment lengths SOLUTION XY = XT + TY Segment Addition Postulate = 39.9 + 39.9 Substitute. = 79.8cm Add.
ALGEBRA Point Mis the midpoint of VW. Find the length of VM . STEP 1 Write and solve an equation. Use the fact that VM = MW. EXAMPLE 2 Use algebra with segment lengths SOLUTION VM= MW Write equation. 4x–1= 3x + 3 Substitute. x – 1 = 3 Subtract 3xfrom each side. x = 4 Add 1 to each side.
STEP 2 Evaluate the expression for VMwhen x =4. So, the length of VMis 15. Check: Because VM = MW, the length of MWshould be 15. If you evaluate the expression for MW, you should find that MW = 15. MW = 3x + 3 = 3(4) +3 = 15 EXAMPLE 2 Use algebra with segment lengths VM = 4x – 1 = 4(4) – 1 = 15
In Exercises 1 and 2, identify the segment bisectorof PQ . Then find PQ. 1. ANSWER MN; 3 3 4 for Examples 1 and 2 GUIDED PRACTICE
In Exercises 1 and 2, identify the segment bisectorof PQ . Then find PQ. 2. 5 ANSWER line l ; 11 7 for Examples 1 and 2 GUIDED PRACTICE
a.FIND MIDPOINTThe endpoints ofRSare R(1,–3) and S(4, 2). Find the coordinates of the midpoint M. EXAMPLE 3 Use the Midpoint Formula
SOLUTION 1 , – , M M = 2 5 a.FIND MIDPOINTUse the Midpoint Formula. 2 The coordinates of the midpoint Mare 1 5 – , 2 2 ANSWER – 3 + 2 1 + 4 2 2 EXAMPLE 3 Use the Midpoint Formula
b.FIND ENDPOINTThe midpoint of JKis M(2, 1). One endpoint is J(1, 4). Find the coordinates of endpoint K. EXAMPLE 3 Use the Midpoint Formula
STEP 1 Find x. STEP 2 Find y. 4+ y 1+ x 1 2 = = 2 2 ANSWER The coordinates of endpoint Kare (3, – 2). EXAMPLE 3 Use the Midpoint Formula SOLUTION FIND ENDPOINTLet (x, y) be the coordinates of endpoint K. Use the Midpoint Formula. 4 + y = 2 1 + x = 4 y =–2 x =3
3. The endpoints of ABare A(1, 2) andB(7, 8). Find the coordinates of the midpoint M. ANSWER (4,5) 4. The midpoint of VWis M(– 1, – 2). One endpoint is W(4, 4). Find the coordinates of endpoint V. ANSWER (– 6, – 8) for Example 3 GUIDED PRACTICE
In the diagram at the right, YWbisects XYZ, and mXYW = 18. Find m XYZ. o By the Angle Addition Postulate, m XYZ =mXYW + m WYZ. BecauseYW bisects XYZyou know thatXYW WYZ. So, m XYW = m WYZ, and you can write m XYZ = m XYW + m WYZ = 18° + 18° = 36°. ~ EXAMPLE 5 Double an angle measure SOLUTION
ANSWER 90° for Example 5 GUIDED PRACTICE 7. Angle MNPis a straight angle, and NQbisects MNP. Draw MNP And NQ. Use arcs to mark the congruent angles in your diagram, and give the angle measures of these congruent angles.