题:边长为1的正方形OABC的顶点O为坐标原点.点A在x轴的正半轴上.点C在y轴的正半轴上.动点D在线段BC上移动(不与
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let BE=x,thus AE=1-x

DE^2=x^2+(1-T)^2

OE^2=x^2+(1-T)^2

DO^2=1+T^2

as DE^2+DO^2=OE^2

x^2+(1-T)^2+1+T^2=1+(1-x)^2

x=T-T^2

s=(BE+CO)/2=(t-t^2+1)/2=-0.5*(t-0.5)^2+0.625

So,when t=0.5 ,s│max=0.625