ABC is an equilateral triangle of side m. P is an external point equidistant from the points A and C, such that:
PA + PB + PC = ( ) m
What is the minimum possible distance one has to cover from P, if one wants to be equidistant from the 3 vertices of ?
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As △ A B C is equilateral, we have:
BD = 2 3 x 3 = 2 3 m
Since P is equidistant from A and C, it will lie on the perpendicular bisector of AC.
Let PA = PC = a
Also, PB = PD + DB
⟹ PB = ( a 2 − ( 2 3 ) 2 ) + 2 3 = ( a 2 − 4 3 ) + 2 3
PA + PB + PC = 3 ( 3 + 2 )
⟹ a + ( a 2 − 4 3 ) + 2 3 + a = 3 ( 3 + 2 )
Solving for a, we get:
a = 3 or a = 2 + 3 5
From G (centroid as well as circumcenter of △ A B C ), the distances from the vertices of the equilateral triangle will be the same. Also, G divides BD in the ratio 2:1.
Since PG should be the minimum possible, a must be equal to 3 .
PG = DG + PD
= [ 3 1 x 2 3 ] + 2 ( 4 a 2 − 3 )
Putting a = 3 , we get:
= 2 1 + 2 ( 1 2 − 3 ) = 2 m