Let I=∫π20log(4+3sinx4+3cosx)dx...(1)⇒I=∫π20log[4+3sin(π2−x)4+3sin(π2−x)]dx⇒I=∫π20log(4+3sinx4+3cosx)dx...(2)
From (1)+(2), we get
2I=∫[log(4+3sinx4+3cosx+log(4+3cosx4+3sinx))]dx=∫π20log[(4+3sinx4+3cosx)×log(4+3cosx4+3sinx)]dx=∫π20(log1)dx=∫π20(0)dx=0