三角函数数列如图,,既然是循环的
a1=cos(π/2+π/3)=-√3/2=-0。5√3
a2=2cos(π+π/3)=2(-1/2)=-1
a3=3cos(3π/2+π/3)=3cos(2π-π/6)=3(√3/2)=1。 5√3
a4=4cos(2π+π/3)=4cosπ/3=4(1/2)=2
a5=5cos(5π/2+π/3)=5(3π-π/6)=5(-cosπ/6)=-2。5√3
a6=6cos(3π+π/3)=6(-cosπ/3)=6(-1/2)=-3
a7=7cos(4π-π/6)=7cosπ/6=7√3/2=3。 5√3
a8=8cos(4π+π/3)=8cosπ/3=8(1/2)=4
a9=9cos(...全部
a1=cos(π/2+π/3)=-√3/2=-0。5√3
a2=2cos(π+π/3)=2(-1/2)=-1
a3=3cos(3π/2+π/3)=3cos(2π-π/6)=3(√3/2)=1。
5√3
a4=4cos(2π+π/3)=4cosπ/3=4(1/2)=2
a5=5cos(5π/2+π/3)=5(3π-π/6)=5(-cosπ/6)=-2。5√3
a6=6cos(3π+π/3)=6(-cosπ/3)=6(-1/2)=-3
a7=7cos(4π-π/6)=7cosπ/6=7√3/2=3。
5√3
a8=8cos(4π+π/3)=8cosπ/3=8(1/2)=4
a9=9cos(4π+5π/6)=9(-cosπ/6)=-9√3/2=-4。5√3
a10=10cos(5π+π/6)=10(-cosπ/6)=-2。
5√3
a11=11cos(6π-π/6)=11cosπ/6=5。5√3
。。。。。。
观察可知Sn是按每4项的和为(1+√3)来循环的,
∵2008÷4=502,即S2008一共有502轮循环,
∴S2008=502(1+√3)
。收起