Triangles ABC and CDA are congruent.
Which angle is equal to angle BAC?
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Triangles ABC and CDA are congruent.
Which angle is equal to angle BAC?
We observe the order of the letters in the congruent triangles and write the matches (from left to right).
That is:
Angle A is equal to angle C.
Angle B is equal to angle D.
Angle C is equal to angle A.
From this, it is deduced that angle BAC (where the letter A is in the middle) is equal to angle C — that is, to angle DCA (where the letter C is in the middle).
C
The triangles ABC and EDC are congruent.
Which angle is equal to the angle \( ∢E \)?
Look at the order of letters in the congruence statement! In , the first letters match (A↔C), second letters match (B↔D), and third letters match (C↔A).
The middle letter shows the vertex of the angle! Angle BAC has vertex A, and since A corresponds to C, we need the angle at vertex C, which is angle DCA.
The order matters! is different from . Always match vertices in the exact order they're written in the congruence statement.
No! The diagram might be misleading or not drawn to scale. Always use the congruence statement to determine which vertices correspond, then find the matching angles.
Use three letters with the vertex in the middle. For angle at vertex A between rays AB and AC, write it as or .
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