10.
11. 8
AnglePairs
LearningObjectives
- Understandand identifycomplementaryangles.
- Understandand identifysupplementaryangles.
- Understandand utilizethe LinearPair Postulate.
- Understandand identifyverticalangles.
Introduction
In this lessonyou will learnaboutspecialanglepairsand provethe verticalanglestheorem,one of the most
usefultheoremsin geometry.
ComplementaryAngles
A pair of anglesareComplementaryanglesif the sum of their measuresis 90º.
Complementaryanglesdo not haveto be congruentto eachother. Rather, their only definingqualityis that
the sum of their measuresis equalto the measureof a right angle:90º. If the outerrays of two adjacent
anglesform a right angle,then the anglesare complementary.
Example 1
The two anglesbeloware complementary.. Whatis the valueof?
Sinceyou knowthat the two anglesmustsum to 90º, you can createan equation.Thensolvefor the variable.
In this case,the variableis.