题目

   Christie Watson was only 17 years old when she walked into the room of a patient. Now, as a    21    , her 20 years in the sickroom has taught Watson that though knowledge of biology and chemistry is    22   , the art of good nursing    23    pure kindness. Watson never forgets two nurses. One nurse     24   tiny spoonfuls of yoghurt to Watson when she was    25    to hospital for an allergic reaction as a child. The other nurse sang Watson's newborn son to    26    at 2 am, and then came back after her    27    had ended ——with a cup如图1，在平面直角坐标系中，A（0，a），C（c，0），△ABC为等腰直角三角形且a、c满足．≥（1）求点B的坐标；（2）如图2，P是直线上的一个动点，是否存在点P使△PAC的面积等于△BAC的面积？若存在，求出P点坐标；若不存在，说明理由；（3）如图3，BF是△ABC内部且经过B点的任一条射线，分别过A作AM⊥BF于M，过 CN⊥BF于N．当射线BF绕点B在△ABC内部旋转时，试探索下列结论：①的值不变；②的值不变．