Calculation: (1-((1/1998))**2)*(1-((1/1997))**2)*(1-((1/1996))**2)*…*( 1-((1/2))**2)*2.
计算：(1-((1/1998))**2)*(1-((1/1997))**2)*(1-((1/1996))**2)*…*(1-((1/2))**2)*2．
<gadget id="calculator">1_999 / 1_998</gadget>
<output>1_999/1_998 = around 1.000501</output>

<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">(1_999/1_998) * (1/2)</gadget>
<output>1_999/3_996 = around 0.50025</output>

<result>1_999/3_996 = around 0.50025</result>