题目

A mother and daughter were rescued from the wreckage (残骸) of a car crash thanks to an app. It can ______ people anywhere in the world using just three ______.Valerie Hawkett, 33, lost ______ of her Ford Fiesta while ______ round a sharp bend in Somerset last October. Ms Hawkett's ______went flying over a bush and landed on its _____ in a field.Her four-year-old ______ Tegan was in the back and the ______ mother called the police to come to her aid — but she didn't know ______ she was.Officers were able to find their way to Ms Hawkett in the field--- after ______ her the link to a website已知：如图，AB是⊙O的直径，C是⊙O上一点，CD⊥AB，垂足为点D，F是的中点，OF与AC相交于点E，AC=8cm，EF=2cm．（1）求AO的长；（2）求sinC的值．