Use angle facts and diagram structure to find unknown angle measures.
Use vertical-angle equality
Problem
\(\text{Two}~\text{lines}\) intersect. \(\text{One}~\text{of}~\text{the}~\text{angles}\) measures \(47°\). What is the measure of the angle directly across from it?
At an intersection, position matters before arithmetic. The target lies directly across the vertex from the labeled angle, so the pair is vertical rather than adjacent. Vertical angles are equal because each is supplementary to the same neighboring angle, allowing the known measure to transfer across the intersection without subtraction.
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