诗歌鉴赏。
                                                                                               诉衷情     陆游     
                                                                                     当年万里觅封侯，匹马戍梁州。
                                                                                     关河梦断何处? 尘暗旧貂裘。
                                                                                     胡未灭，鬓先秋，泪空流。
                                                                                     此生谁料，心在天山，身老沧洲。

圆的周长公式C=____；圆的面积公式S=____.