本题不接受通过精确作图得出的解答。 图中显示了一个等腰三角形 PQR,其中 。三角形的顶点为 P(k, 4)、Q(5, 3) 和 R(9, 10)。

- (i)
求 k 的值。
- (ii)
过点 Q 作直线交 y 轴于点 S,使得 。
求直线 QS 的方程和点 S 的坐标。
- (iii)
求三角形 PQR 的面积与四边形 PQRS 的面积之比。
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完整解法
10(i)
1. Calculate the square of the length of QR
2. Express the square of the length of PQ in terms of k and equate to $QR^2$
Since , .
3. Solve the quadratic equation for k
4. Determine the correct value of k based on the diagram
From the diagram, point P is to the left of the y-axis, so its x-coordinate must be negative ().
Therefore, .
10(ii)
1. Find the coordinates of P from part (i) using the given $PQ = QR$.
Using the distance formula for :
From the diagram, P is to the left of the y-axis, so . Thus, and is .
2. Set up an equation for the coordinates of S using $PS = SR$.
Since S lies on the y-axis, let its coordinates be .
Given , we have :
3. Solve for y to find the coordinates of S.
The coordinates of S are .
4. Find the equation of the line QS.
Using and :
Gradient of QS,
Since S is the y-intercept, the equation of QS is:
Coordinates of S:
Equation of QS:
10(iii)
1. Find the coordinates of P and S from earlier parts
From part (i), is .
From part (ii), is .
The coordinates of the vertices are , , and .
2. Calculate the area of triangle PQR
Using the shoelace formula for with vertices , , :
3. Calculate the area of quadrilateral PQRS
Using the shoelace formula for quadrilateral with vertices , , , :
4. Find the ratio of the areas
Dividing by 15:
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