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共回答了14个问题采纳率:92.9% 举报
有图么?
OA ⊥ OB
OB = ±√(AB^2 - OA^2) = ±4
A是(3,0)还是(-3,0)?
B是(0,4)还是(-4,0)?
我当A是(3,0),B是(0,4)那样做吧
1.设AB为 y = kx + b
代入AB得
k = -4/3 ,b = 4
即AB为y = (-4/3)x + 4
为以下问题好解,先求P,Q与 t 的关系式
Q = (XQ,YQ)
∵YQ / QA = BO / AB = 4 / 5
∴YQ = (4 / 5) QA = (4 / 5) t
∵XQ / QA = AO / AB = 3 / 5
∴XQ = 3 - (3 / 5) QA = 3 - (3 / 5) t
P = (OA,0)
当t 3时
P = (AO - AP,0) = ( [3 - (t - 3)],0 ) = ((6 - t),0)
2.S△APQ = (OA - OP) * (YQ) = (OA - XP) * (YQ)
当t 3 时(t < 5)时
S△APQ = (4 / 5) t * (t - 3)
即S△APQ = (4 / 5) t * | t - 3 |
3.1 当四边形QBED为直角梯形,∠QDE为直角
要么∠BQD为直角,要么∠BED为直角
分析下表
+-----------------+-----------------------+------------------
| | ∠BQD为直角 | ∠BED为直角
+-----------------+-----------------------+------------------
| 0
1年前
4