I can't install CUDA 5.0 on my macbook pro

I’m a student who starts to learn CUDA programming. But I can’t install the CUDA toolkit on my macbook pro retina 15 successfully . I’ve checked the installing instruction, and I have installed the gcc from Xcode. However, it only took me about 1 minute to install cuda_5.0.36_macos.pkg which not seems like reasonable. In fact, I can’t find the nsight eclipse and other softwares , and there is no sample in ./Developer/NVIDIA/CUDA-5.0/. It’s my first time to use OS X and I don’t know how to solve the problem now.