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chapter0.4r
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à 0.4ïCongruent Triangles
äïPlease determine if the following pairs of triangles
êêare congruent.
âSèDetermine if the given triangles are congruent.
êêêThe two triangles, triangle ABC and triangle
êêêFED, are congruent by the SAS Rule.
@fig0401.bmp,25,118
éS Two triangles are congruent it they have the same size and
shape.ïIn the previous section, we looked at similar triangles which
only have to have the same shape.ïThis means that congruent triangles
have the same angles and sides, whereas similar triangles just have
the same angles.
è It is not necessary to check all three sides and all three angles
in order to determine if two triangles are congruent.ïYou can deter-
mine congruence by establishing that corresponding sides are equal in
length, by showing that two corresponding angles and the included side
are equal, or by showing that two sides and the included angle are
equal.ïThe three rules used to determine if two triangles are congruent
are given below.
è 1)ïSSS Rule (Side-Side-Side)ïTwo triangles are congruent if the
three sides of one triangle equal the corresponding sides of a second
triangle.
è 2)ïSAS Rule (Side-Angle-Side)ïIf two sides and the included angle
of one triangle equal two sides and the included angle of a second tri-
angle, the two triangles are congruent.
è 3)ïASA Rule (Angle-Side-Angle)ïIf two angles and the included side
of one triangle equal two angles and the included side of a second tri-
angle, the two triangles are congruent.
è These three rules imply that if one of the three conditions is met,
then all remaining sides and angles of one triangle must equal the
corresponding sides and angles of the other triangle. This says that
the triangles are identical, and in a sense there is just one distinct
triangle.
è It is interesting to note that in trigonometry ç same conditions
are sufficient to be able to solve a given triangle.ïFor example, in
a later chapter on oblique triangles we will use the Law of Cosines to
solve a given triangle when we know three sides or when we know two
sides and the included angle.ïWe will use the Law of Sines to solve a
given triangle when we know two angles and the included side.ïA fourth
condition, one angle and two sides with one side opposite the given
angle, will also be covered.
1ê Determine if the triangles are congurent.
êêêêè A)ïSSSêêïB)ïASA
êêêêè C)ïSASêêïD)ïNot congruent
@fig0402.bmp,25,229
ü
êë These two triangles are congruent by the SSS Rule.
Ç A
2ê Determine if the triangles are congruent.
êêêêè A)ïSSSêêïB)ïASA
êêêêè C)ïSASêêïD)ïNot congruent
@fig0403.bmp,25,229
ü
êêThe two triangles are congruent by the SAS Rule.
Ç C
3ê Determine if the triangles are congruent.
êêêêè A)ïSSSêêïB)ïASA
êêêêè C)ïSASêêïD)ïNot congruent
@fig0404.bmp,25,229
ü
êêThe triangles are congruent by the ASA Rule.
Ç B
4ê Determine if the triangles are congruent.
êêêêè A)ïSSSêêïB)ïASA
êêêêè C)ïSASêêïD)ïNot congruent
@fig0405.bmp,25,229
ü
êêThe triangles are congruent by the SAS Rule.
Ç C
5ê Determine if the triangles are congruent.
êêêêè A)ïSSSêêïB)ïASA
êêêêè C)ïSASêêïD)ïNot congruent
@fig0406.bmp,25,229
ü
êë The triangles are congruent by the SSS Rule.
Ç A
6ê Determine if the triangles are congruent.
êêêêè A)ïSSSêê B)ïASA
êêêêè C)ïSASêê D)ïNot congruent
@fig0407.bmp,25,229
ü
êê The triangles are congurent by the ASA Rule.
Ç B
7ïTriangle ABC and triangle DEF are given.ïIf angle C equals
êè angle E, AC = EF, and BC = DE, are the triangles congruent?
êêè A)ïSSSêêèB)ïASA
êêè C)ïSASêêèD)ïNot
êêêêêêè congruent
ü
êêThe triangles are congurent by the SAS Rule.
@fig0408.bmp,3500,980
Ç C
8ïTriangle PQR and triangle TUV are given.ïIf angle R equals
angle T, angle Q equals angle V, and angle P equals angle U, are the
triangles congruent?
êêè A)ïSSSêêèB)ïASA
êêè C)ïSASêêèD)ïNot necessarily
êêêêêêè congruent
ü
êêèThe two triangles are not necessarily
êêècongruent.
@fig0409.bmp,3500,980
Ç D
9ïTriangle HRS and triangle LMN are given.ïIf angle R equals
êè angle L, RS = LM, and HS = MN, are the triangles congruent?
êêêA)ïSSSêêïB)ïASA
êêêC)ïSASêêïD)ïNot necessarily
êêêêêêë congruent
ü
êëThe two triangles are not necessarily congruent.
@fig0410.bmp,3500,980
Ç D