图中的图象显示了曲线 的一部分。A 是曲线上的一个点,且 A 的 x 坐标为 2。曲线在点 A 处的法线与 x 轴交于点 B。

- (a)
求曲线在点 A 处的法线方程。

- (b)
求由法线 、曲线、x 轴和 y 轴所围成的阴影区域的面积。
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完整解法
13(a)
1. Find the $y$-coordinate of point A
When ,
So, point A is .
2. Differentiate the equation of the curve to find the gradient function
3. Find the gradient of the tangent at A
At ,
4. Find the gradient of the normal and its equation
Gradient of normal
Equation of the normal at :
13(b)
1. Find the equation of the normal at A and the coordinates of B (from part a).
At , .
Gradient of normal .
Equation of normal: .
At , . So is .
2. Set up the expression for the total shaded area.
The shaded area is the sum of the area under the curve from to and the area of the triangle formed by the normal from to .
3. Evaluate the definite integral for the area under the curve.
4. Calculate the area of the triangle and the total area.
or (to 3 s.f.)
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