@ @WW@ @†a‡Èÿa@ @ . 49 ( ) 35 ( ) 32 ( ) 7 () x +y y x [AMC82009] ( ) . 360y 360x 165 ( ) 115 ( ) 85 ( ) 80 ( ) 0 ) DC B A [AMC82009] ( ) ) 9() (9 AB AB −C A +C A A DA D 7( ) 6( ) 5 () [AMC82010] ( . 8 11 AMC 8 .9 AMC 8 29 ( ) 28 ( ) 27 ( ) 26 ( )