
Christopher R. answered 11/26/14
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Latika, f(x)=sinx has a period of 2pi. This indicates f(x)=f(x+2pi) and f(x+4pi)=f(x+2*2pi)=f(x). Therefore, f(a)=f(a+2pi)=f(a+4pi)=-(1/9)
Thus, f(a)+f(a+2pi)+f(a+4pi)=-(1/9)+-(1/9)+-(1/9)=-(3/9)=-1/3
Hope this helps.