If the equation of an... - Circles

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Q.) If the equation of any two diagonals of a regular pentagon belongs to family of lines (1+2a)y-(2+a)x+1-a-0 and their lengths are sin 36°, then locus of centre of circle circumscribing the given pentagon (the triangles formed by these diagonals with sides of pentagon have no side common) is

[A]x² +y²-2x-2y+1+sin² 72°=0

[B]x²+y²-2x-2y + cos² 72°=0

[C]x²+2x-2y+1+cos² 72°-0

[D]x²+y²-2x-2y+sin² 72°-0

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