http://www.ck12.org Chapter 4. Triangles and Congruence
DE=
√
( 3 − 6 )^2 +( 9 − 4 )^2
=
√
(− 3 )^2 +( 5 )^2
=
√
9 + 25
=
√
34
EF=
√
( 6 − 10 )^2 +( 4 − 7 )^2
=
√
(− 4 )^2 +(− 3 )^2
=
√
16 + 9
=
√
25 = 5
DF=
√
( 3 − 10 )^2 +( 9 − 7 )^2
=
√
(− 7 )^2 +( 2 )^2
=
√
49 + 4
=
√
53
No sides have equal measures, so the triangles are not congruent.
Know What? RevisitedFrom what we have learned in this section, the two triangles are not congruent because the
distance from the fridge to the stove in your house is 4 feet and in your neighbor’s it is 4.5 ft. The SSS Postulate
tells us that all three sides have to be congruent.
Review Questions
Are the pairs of triangles congruent? If so, write the congruence statement.