题目

It all started at the beginning of this term. At first, Carmen wasn’t really sure what was happening. In class, she had to squint (眯眼) to see the blackboard clearly. As it got worse, she became more and more worried. It was important for her to see the notes and homework the teacher wrote on the board. In class, she asked for a desk that was closer to the blackboard. One day, her teacher said, “Carmen, I’ve noticed you squinting a lot. Are you having trouble seeing the board?” Carmen shook her head. “I’m fine, Mrs. Cruz.” At home, she had to sit closer and closer to（12分）已知双曲线C以椭圆的焦点为顶点，顶点为焦点（1）求双曲线C的标准方程；（2）若双曲线C的左、右两焦点分别为F1、F2，P为双曲线C左支上一点，若求S△PF1F2