基于chebyshev的水声信号分析，实现用SDRAM运行nios，同时用SRAM保存摄像头数据，该函数用来计算任意函数的一阶偏导数(数值方法)。- Based chebyshev underwater acoustic signal analysis, Implemented with SDRAM run nios, while saving camera data SRAM, This function is used to calculate the arbitrary function