If lengths if ( p1 , p2 ) and ( p1 , p3 ) are same , then following conditions must met to form a square . 1 ) Square of length of ( p1 , p4 ) is same as twice the square of ( p1 , p2 ) 2 ) Square of length of ( p2 , p3 ) is same as twice the square of ( p2 , p4 )
if ( d2 == d3 && 2 * d2 == d4 && 2 * distSq ( p2 , p4 ) == distSq ( p2 , p3 ) ) { return true ; }