Geometry Problem
Level: Mathematics Education, High School, Honors Geometry, College.
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Wednesday, November 30, 2011
Problem 694: Triangle, Angles, 30 Degrees, Auxiliary Construction, Mind Map, Polya
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Draw a perpendicular BF from B to AC intersecting CD in E, join AE. Since Tr ABC is isosceles, EA =EC and therefore /_EAC=30 hence /_DAE=18 or AD is angle bisector of /_BAE. Now /_AEF=60=/AED and thus /_DEB=60 so ED bisects /_AEB which means BD bisects /_ABE. So /_x =12
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