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chapter0.3r
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1995-04-09
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à 0.3ïSolving Similar Triangles
äïPlease find the indicated side of the following similar
êêtriangles.
âèSolve for "x" in the given similar triangles.
êêê6ë x
#êêê─ï=ï──ë6 ∙ 24 = 8 ∙ xè 144 = 8x
êêê8ë24êêêï18 in. = x
êêêêë The unknown side is equal to 18 in.
@fig0301.bmp,25,118
éS
Two triangles are similar if they have the same shape but not necessar-
ily the same size.ïThis means that corresponding angles are equal, but
corresponding sides might be of different lengths.ïOne thing that is
true about similar triangles is that "ratios of corresponding sides are
proportional."ïThis means we can set up a proportion to find the unknown
side.ïIn our example, we can set up a proportion involving correspond-
ing sides.
êêë 6 in.è xëThe proportion can beë 6∙24 = 8∙x
#êêë ──── = ────è solved to find the miss-è 144 = 8x
êêë 8 in.è24 in. ing side, "x".êë18 in. = x
êêë Thus, the missing side is x = 18 in.
@fig0302.bmp,5,165
êêë The fact that ratios of corresponding
êêë sides of similar right triangles are equal
êêë will help us in trigonometry.ïWe will later
êêë define the sine of an angle, φ, in a right
êêë triangle to be the ratio of the side opposite
êêë the angle, φ, and the hypotenuse.ïThis ratio
êêë must be equal to the corresponding ratios of
êêë all other right triangles with the angle, φ,
êêë no mater how large the triangle.ïThis
êêë means that the sine of any fixed angle, say
#êêë 30ò, is constant, and we can make a list or
êêë trig. table for the sine of any angle.ïThus,
êêë trig. tables are based on this property of
êêë similar triangles that ratios of corresponding
êêë sides are equal.
1ê Solve for "x" in the given similar triangles.
êêêêè A)ï24êêèB)ï20
êêêêè C)ï22êêèD)ïå
@fig0303.bmp,25,229
ü
êë 12ë18
#êë ──ï=ï──ë 12x = (16)(18)ë 12x = 288
êë 16ë xêêêêx = 24
Ç A
2ê Solve for "x" in the given similar triangles.
êêêêè A)ï6êêè B)ï10
êêêêè C)ï8êêè D)ïå
@fig0304.bmp,25,229
ü
êê2ë 4
#êê─ï=ï──ë (2)(12) = 4∙xê 24 = 4x
êêxë12êêêê6 = x
Ç A
3ê Solve for "x" in the given similar triangles.
êêêêè A)ï4.5êêïB)ï5.76
êêêêè C)ï6êêè D)ïå
@fig0305.bmp,25,229
ü
êê4ë8
#êê─ï=ï─ê 4x = (3)(8)êï4x = 24
êê3ëxêêêê x = 6
Ç C
4ê Solve for "x" in the given similar triangles.
êêë (round to the nearest hundredth)
êêêêè A)ï10 in.êêB)ï12.2 in.
êêêêè C)ï9.6 in.êë D)ïå
@fig0306.bmp,25,229
ü
êê4ë6.4
#êê─ï=ï───ë 4x = (6)(6.4)ê4x = 38.4
êê6ë xêêêêx = 9.6 in.
Ç C
5ê Solve for "x" in the given similar triangles.
êêêêè A)ï38 in.êêB)ï39.6 in.
êêêêè C)ï36 in.êêD)ïå
@fig0307.bmp,25,229
ü
êë 10ë22
#êë ──ï=ï──ë 10x = (18)(22)ë 10x = 396
êë 18ë xêêêêx = 39.6
Ç B
6ê Solve for "x" in the given similar triangles.
êêë (round answer to the nearest hundredth)
êêêêè A)ï26êêèB)ï28
êêêêè C)ï24êêèD)ïå
@fig0308.bmp,25,229
ü
êè 2 ft.ë8 ft.
#êè ────ï=è────ë2x = (6)(8)êè2x = 48
êè 6 ft.ëx ft.êêêëx = 24
Ç C
7ê Solve for "x" in the given similar triangles.
êêë (round answer to the nearest hundredth)
êêêêè A)ï6.2 cm.êë B)ï6.32 cm.
êêêêè C)ï5.41 cm.êëD)ïå
@fig0309.bmp,25,229
ü
êè2.3 cmë6.8 cm
#êè──────ï=ï──────ë2.3(16) = 6.8xè 36.8x = 6.8x
êè5.41 cmè 16 cmêêêè5.41 cm. ≈ x
Ç C
8ê Solve for "x" in the given similar triangles.
êêë (round answer to the nearest hundredth)
êêêêè A)ï17.74 m.êëB)ï16.28 m.
êêêêè C)ï15.3 m.êë D)ïå
@fig0310.bmp,25,229
ü
êë2.3ë x
#êë───ï=ï──ë (2.3)(27) = 3.5xë 62.1 = 3.5x
êë3.5ë27êêêê17.74 m. = x
Ç A
9ê Solve for "x" in the given similar triangles.
êêë (round answer to the nearest hundredth)
êêêêè A)ï4.1êêïB)ï3.79
êêêêè C)ï5.23êê D)ïå
@fig0311.bmp,25,229
ü
êë xë 64
#êè ────ï=ï──ë 42x = (2.49)(64)è 42x = 159.36
êè 2.49ë42êêêêx = 3.79
Ç B
10êSolve for "x" in the given similar triangles.
êêêêè A)ï50êêèB)ï32
êêêêè C)ï28êêèD)ïå
@fig0312.bmp,25,229
ü
êê2ë25
#êê─ï=ï──ê 2x = 4∙25êè2x = 100
êê4ë xêêêêx = 50
Ç A