licheng_lu
幼苗
共回答了24个问题采纳率:83.3% 举报
(1)∠AOD=45°,OD=2√2,当点P移动到点D时,t=√2.
(2)t秒时P(t√2,t√2),Q(2t,0),B(6,2).
△PQB为直角三角形,画示意图知,PB^2=PQ^2+BQ^2,
(t√2-6)^2+(t√2-2)^2=[(2-√2)^2+2]t^2+(2t-6)^2+4,
4t^2-16√2t+40=(8-4√2)t^2+4t^2-24t+40,
(8-4√2)t^2=(24-16√2)t,t>0,
∴t=(3√2-4)/(√2-1)=(3√2-4)(√2+1)=2-√2,为所求.
1年前
10