设函数f(x)=x(0≤x≤π)展开成正弦级数为∑n=1∞bnsinnx,求系数b7.
b7=2/π∫0πf(x)sin7xdx =2/π∫0πxsin7xdx =2/(7π)(-[xcos7x]0π+∫0πcos7xdx) =2/(7π)(π+1/7[sin7x]0π)=2/7
设函数f(x)=x(0≤x≤π)展开成正弦级数为∑n=1∞bnsinnx,求系数b7.
b7=2/π∫0πf(x)sin7xdx =2/π∫0πxsin7xdx =2/(7π)(-[xcos7x]0π+∫0πcos7xdx) =2/(7π)(π+1/7[sin7x]0π)=2/7