Use angle facts and diagram structure to find unknown angle measures.
Translate angle words into angle structure
Problem
At \(B\), \(BA\) and \(BC\) form a straight path, and ray \(BD\) splits it into adjacent angles \(\angle~ABD\) and \(\angle~DBC\). Write the angle relationship, and name the angle fact.
Big Picture
What this problem is really about
Treat the straight path as one whole angle, then view the extra ray as dividing that whole into two adjacent, nonoverlapping parts. Angle addition says the measures of the parts equal the measure of the whole. Naming the straight-angle fact supplies the total without assuming the split creates equal angles.
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