图示桁架受水平外力P作用，各杆刚度EA相同，则BC杆转角为<img src="https://static.zxtiku.com/wangke/imgs/topic/ea0ff47de96b1c48c3f7c3dbdf116d29.jpg"/><br/> A、<img src="https://static.zxtiku.com/wangke/imgs/topic/98c241919bf2b463783ef9b96de66b3b.jpg"/><br/> B、<img src="https://static.zxtiku.com/wangke/imgs/topic/4668c9b36e175595985a670679cf39a1.jpg"/><br/> C、<img src="https://static.zxtiku.com/wangke/imgs/topic/65a5971f6f75f22d06c5ed0fd7afe09e.jpg"/><br/> D、<img src="https://static.zxtiku.com/wangke/imgs/topic/fffa4dd7a96d3ec711ccf4f68ffbbc1c.jpg"/>