图中显示了 ΔABC。

- (i)
May说直线 AC 与 y 轴相交于 3.2。请展示你会如何检验她的说法是否正确。
答
- (ii)
求 AB 的长度。
答:___ 单位
- (iii)
在不计算任何角的值的情况下,求 cos ÂBC 的值。
答:cos ÂBC = ___
- (iv)
点 P 在直线 y = 1 上。已知 ΔABC 的面积 : ΔAPB 的面积 = 4: 3,求 P 的两个可能的 x 坐标。
答:x = ___ 或 ___
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完整解法
10 (a)(i)
1. Find the gradient of line AC from the two given coordinates.
For and ,
2. Find the y-intercept of AC and check May's claim.
Using and point ,
So the line intersects the -axis at .
May is incorrect, since line intersects the -axis at , not .
10 (a)(ii)
1. Find the horizontal and vertical differences between A and B.
and
Horizontal difference:
Vertical difference: , so the vertical distance is .
2. Apply the distance formula to find AB.
units
10 (a)(iii)
1. Identify the adjacent side and hypotenuse for the angle at $B$, noting that the angle is obtuse.
From to , the horizontal change is units left and the vertical change is units up, so units.
Since is horizontal to the right, is obtuse. Hence
10 (a)(iv)
1. Compare the areas using the bases on the same horizontal line.
Since , and lie on , triangles and have the same perpendicular height from .
Therefore,
Given
so
2. Find the possible positions of $P$ from the required length $BP$.
From the coordinates, and , so
Since
As lies on , it is 3 units horizontally from , whose -coordinate is 2.
Hence
or
or
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