Z7-I-5 MO 2017

Prokop constructed a triangle ABC whose interior angle at vertex A was greater than 60° and whose interior angle at vertex B was less than 60°. Juraj drew, in the half-plane determined by line AB and point C, a point D such that triangle ABD was equilateral. The boys then found that triangles ACD and BCD are isosceles with apex vertex D. Determine the measure of angle ACB.

Final Answer:

x =  30 °

Step-by-step explanation:

x = ACB y = DCB = CBD z = ADC  ADB = 60° CD = AD = DB = AB = a DAC = DCA = x+y  BCD: 2y+60 +z = 180 ACD: 2(x+y)+z = 180  2y+z = 120 2x+2y+z = 180  2x+120=180 x=(180120)/2=30



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Calculation of an isosceles triangle.
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geometryalgebraplanimetricsUnits of physical quantitiesthemes, topicsGrade of the word problem

 
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