本题中通过精确作图得出的解答将不予采纳。 图(未按比例绘制)显示了一个梯形 OPQR,其中 平行于 且 。点 和 的坐标分别为 和 ,且 是原点。

- ((i))
求 的坐标。

- ((ii))
PQ 与 y 轴交于点 T。证明三角形 ORT 是等腰三角形。
- ((iii))
点 S 满足 ORPS 构成一个平行四边形。
求 S 的坐标。
- ((iv))
求梯形 OPQR 的面积。
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完整解法
12((i))
1. Find the gradient of the line OR
Gradient of
2. Find the equation of the line PQ
Since , gradient of .
Using point :
3. Find the gradient of the line RQ
Since , .
Gradient of
4. Find the equation of the line RQ
Using point :
5. Solve the equations simultaneously to find the coordinates of Q
Equating the two expressions for :
Substitute into :
The coordinates of are .
12((ii))
1. Find the gradient of OR and the equation of line PQ.
Gradient of .
Since , gradient of .
Equation of passing through :
2. Find the coordinates of T.
Since is the y-intercept of , let .
.
Coordinates of are .
3. Calculate the lengths of OT, OR, and RT to show two sides are equal.
Length of units.
Length of .
Length of .
Since , triangle is isosceles.
Triangle ORT is isosceles since .
12((iii))
1. Equate the midpoints of the diagonals of the parallelogram
In parallelogram , the diagonals and bisect each other. Therefore, their midpoints are the same.
Let the coordinates of be .
Midpoint of = Midpoint of
2. Solve for the coordinates of S
Equating the -coordinates:
Equating the -coordinates:
The coordinates of are .
12((iv))
1. Apply the shoelace formula using the coordinates of the vertices in order
Using the coordinates , , (from part (i)), and in counter-clockwise order:
2. Evaluate the expression to find the area
units
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