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问题: 关于三角函数的

若f(n)=sin(nπ/6),n∈N+,则f(1)+f(2)+L+f(2008)=

解答:

若f(n)=sin(nπ/6),n∈N+,则f(1)+f(2)+...+f(2008)=

f(1)+f(11) = sin(π/6)+sin(11π/6) = sin(π/6)-sin(π/6) = 0
f(2)+f(10) = sin(2π/6)+sin(10π/6) =sin(2π/6)-sin(2π/6)=0
...
f(5)+f(7) = sin(5π/6)+sin(7π/6) = sin(5π/6)-sin(5π/6) = 0
f(6)+f(12) = sin(π)+sin(2π) = 0

--->f(1)+f(2)+...+f(12) = 0
∵f(13)+f(14)+...+f(24) = f(1)+f(2)+...+f(12) = 0 ...
且2008÷12=167...4

--->f(1)+f(2)+...+f(2008) = 167*0 + f(1)+f(2)+f(3)+f(4)
 = sin(π/6)+sin(2π/6)+sin(3π/6)+sin(4π/6)
 = 1/2 + √3/2 + 1 + √3/2
 = 3/2 + √3