Question

循环数列1,2,3,4,1,2,3,4.的通项公式是什么?

Answer 1

An=2.5-SIN((2n-1)/4)×(COS((2n-1)/4)+2^0.5)

由SIN((2n-1)/4)得出(1/2)^0.5,(1/2)^0.5,-(1/2)^0.5,-(1/2)^0.5

由COS((2n-1)/4)+2^0.5得出3/2×2^0.5,1/2×2^0.5,1/2×2^0.5,3/2×2^0.5

相乘得1.5,0.5,-0.5,-1.5

用2.5减去的1,2,3,4

反复循环