题目

SYDNEY: As they sat sharing sweets beside a swimming pool in 1999. Shane Gould and Jessicah Schipper were simply getting along well, chatting about sport, life and anything else that came up. Yet in Sydney next month, they will meet again by the pool, and for a short time the friends will race against each other in the 50 – meter butterfly in the Australian championships at Homebu Bay. Gould, now a 47 – year – old mother of four, has announced she will be making a return to elite competition (顶级赛事) to swim the one event, having set a qualifying (合格的)time of 30. 32 seconds i等腰三角形的顶角比底角大9°，则这个三角形顶角的度数是_________________。