(1+(1/2))*(1-(1/2))*(1+(1/3))*(1-(1/3))*(1+(1/4))* (1-(1/4))*…*(1+(1/2004))*(1-(1/2004))
(1+(1/2))*(1-(1/2))*(1+(1/3))*(1-(1/3))*(1+(1/4))*(1-(1/4))*…*(1+(1/2004))*(1-(1/2004))
<gadget id="calculator">1 / 2</gadget>
<output>1/2 = around 0.5</output>

<gadget id="calculator">2_005 / 2_004</gadget>
<output>2_005/2_004 = around 1.000499</output>

<gadget id="calculator">(1/2) * (2_005/2_004)</gadget>
<output>2_005/4_008 = around 0.50025</output>

<result>2_005/4_008 = around 0.50025</result>