Наити производную: (1+sin3x)/cos3x
[(1+sin3x)' cos3x-(1+sin3x)(cos3x)']/cos²3x=[3cos3xcos3x+3sin3x(1+sin3x)]/cos²3x=[3cos²3x+3sin²3x+3sin3x]/cos²3x=[3+3sin3x]/cos²3x