4.2.3 Triangle Congruence: CPCTC (continued) Example 4 Using CPCTC in a Proof: Another Example
Remember, when given a figure on a coordinate plane, the lengths of the figure’s sides can always be determined by using the distance formula. For this proof, first find the length of each side of △ ABC and of △ DEF by using the distance formula. Then, since DF = AC , EF = BC , and DE = AB , the two triangles are congruent by SSS. So, since ∠ BCA and ∠ DFE are corresponding angles, ∠ BCA ≅ ∠ DFE by CPCTC.
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