CPCTC

“CPCTC” is an acronym which stands for “corresponding parts of congruent (http://planetmath.org/Congruent2) triangles (http://planetmath.org/Triangle) are congruent.” In other , if

$\mathrm{△}ABC\cong \mathrm{△}DEF,$(1)

then all of the following are true:

• $\mathrm{\angle }A\cong \mathrm{\angle }D$;

• $\overline{AB}\cong \overline{DE}$;

• $\mathrm{\angle }B\cong \mathrm{\angle }E$;

• $\overline{BC}\cong \overline{EF}$;

• $\mathrm{\angle }C\cong \mathrm{\angle }F$;

• $\overline{AC}\cong \overline{DF}$.

Note.  The notation in (1) indicates that the isomorphism in question maps $A\mapsto D$,  $B\mapsto E$,  and  $C\mapsto F$.