[单选题]信号f1(t)=cos(4πt), f2(t)=u(t+τ)−u(t−τ), f(t)=f1(t)f2(t),则f(t)的傅里叶变换结果为sjp答案窝(daanwo.com)-大学生作业答案及考资分享平台
ASa(w+4π)+Sa(w−4π)sjp答案窝(daanwo.com)-大学生作业答案及考资分享平台
BSa(w+4π)−Sa(w−4π)sjp答案窝(daanwo.com)-大学生作业答案及考资分享平台
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