Let .

Prove that

Author: Van Khea, Cambodia

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Let be circumcenter of triangle .

Prove that:

Author: Van Khea, Cambodia

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Let be midpoints of an equilateral triangle . Let be midpoint of . Prove that:

Author: Van Khea, Cambodia

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is an equilateral triangle.

is midpoints of and

Prove that

Proposed by Van Khea, Cambodia

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Let be circumcenter of an equilateral triangle and let be point lie on incircle. Prove that:

Author: Van Khea, Cambodia

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Let be point lie on circumcircle of an equilateral triangle . Let

Prove that

Author: Van Khea, Cambodia

Filed under: Uncategorized ]]>

Let be point lie on circumcircle of an equilateral triangle .

Let be projection points from to .

Prove that

Prove that

Author: Van Khea, Cambodia

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Let be point lie on of . Let and be incenters of and . Let be circumcenters of .

Prove that are collinear.

Author: Van Khea, Cambodia

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Given an equilateral triangle . Let be point on . Let and be incenter of and . Let be circumcenter of .

Prove that is an equilateral triangle.

Author: Van Khea, Cambodia

Filed under: Uncategorized ]]>

Prove that .

Author: Van Khea, Cambodia

Filed under: Uncategorized ]]>