f(-4/3)=f(-4/3+1)+1
=f(-1/3)+1
= 【f(-1/3+1)+1】+1
=f(2/3)+2
=-cos[π*(2/3)] +2
=1/2+2
=5/2
f(4/3) =-cos[π*(4/3)]=1/2,
则f(4/3)+f(-4/3)=5/2+1/2=3.
f(-4/3)=f(-4/3+1)+1
=f(-1/3)+1
= 【f(-1/3+1)+1】+1
=f(2/3)+2
=-cos[π*(2/3)] +2
=1/2+2
=5/2
f(4/3) =-cos[π*(4/3)]=1/2,
则f(4/3)+f(-4/3)=5/2+1/2=3.