鏁板?棰樻垜涓嶄細濡傚浘鎵€绀?宸茬煡鈻矨BC涓?AB=6,AC=9,AD鈯?C浜嶥,M涓篈D涓婁换涓€鐐?鍒橫C2-MB2绛変簬A. 9 B. 35 C. 45 D. 鏃犳硶璁＄畻告诉我怎么做

MC2-MB2=DC^2-BD^2
DC^2=AC^2-AD^2
BD^2=AB^2-AD^2
所以MC2-MB2=DC^2-BD^2=AC^2-AB^2=45

图呢?

选C.
MC2=MD2+CD2,MB2=MD2+BD2,
MC2-MB2=CD2-BD2,
CD2=AC2-AD2,
BD2=AB2-AD2,
CD2-BD2=AC2-AB2=45

D