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Geometry ProblemLevel: Mathematics Education, High School, Honors Geometry, College.Click the figure below to see the complete problem 855.
The perpendicular from point B, to the AC meet AD at point E. Because AC, it's height and bisector of the triangle ABE, is isosceles. So, angle AEB= 77 degrees. The triangle BEC , is equilateral. So ,angle DBE =86-60=26 degrees ,therefore angle BDE=77 degrees .Then, BD=BE=BC .So ,from the triangle BDC , 86+2(30+X)=180 .So, x=17 degreesPlan: http://img832.imageshack.us/img832/3616/p855triangleangle30degr.gif
Generalizare:Fie ABE un triungi isoscel AB=AE cu m( x= 30-13=17