Why does SSS work?
Why does SAS work?
Why does ASA work?
When does SSA work?
http://www.illustrativemathematics.org/illustrations/110
http://www.illustrativemathematics.org/illustrations/109
http://www.illustrativemathematics.org/illustrations/339
http://www.illustrativemathematics.org/illustrations/340
Triangle Congruence
SSS
SAS
ASA & AAS
HL
http://www.ck12.org/geometry/Triangle-Congruence/
http://www.ck12.org/geometry/SSS-Triangle-Congruence/
http://www.ck12.org/geometry/SAS-Triangle-Congruence/
http://www.ck12.org/geometry/ASA-and- AAS-Triangle-Congruence/
http://www.ck12.org/geometry/HL-Triangle-Congruence/
ASA
AAS
Not AAA
Not SSA
http://www.mathopenref.com/congruentsss.html
http://www.mathopenref.com/congruentsas.html
http://www.mathopenref.com/congruentasa.html
http://www.mathopenref.com/congruentaas.html
http://www.mathopenref.com/congruenthl.html
http://www.mathopenref.com/congruentaaa.html
http://www.mathopenref.com/congruentssa.html
SSS & SAS
Not AAA & Not SSA
http://www.youtube.com/watch?v=21of921lRKo
http://www.youtube.com/watch?v=q6CpJAuNBaE
http://www.youtube.com/watch?v=DWWwo4l_s9g