Number of solutions of the equation sinxcos3x+sin3xcos9x+sin9xcos27x=0 in the interval 0,π4 is
sinxcos3x+sin3xcos9x+sin9xcos27x=0
or 2sinxcosx2cos3xcosx+2sin3xcos3x2cos9xcos3x+2sin9xcos9x2cos27xcos9x=0or sin(3x−x)2cos3xcosx+sin(9x−3x)2cos9xcos3x+sin(27x−9x)2cos27xcos9x=Cor (tan3x−tanx)+(tan9x−tan3x)+(tan27x−tan9x)=0or tan27x−tanx=0or tanx=tan27x⇒27x=nπ+x,n∈Ior x=nπ26,n∈I.x=π26,2π26,3π26,4π26,5π26,6π26
Hence, there are six solutions