如图所示,这是一个中间空心的圆柱体,厚度为 10 cm。(取 。)

- (a)
求阴影面的面积。
- (b)
兰德尔将整个圆柱体浸入红漆中。圆柱体被染成红色的表面积是多少?
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完整解法
12(a)
1. Find the outer and inner radii of the shaded face
Outer radius
Inner radius
2. Calculate the area of the shaded face
答案
12(b)
1. Calculate the area of the two annular bases (top and bottom faces).
Area of one annular face
Area of two faces
2. Calculate the outer and inner curved surface areas.
Outer curved surface area
Inner curved surface area
3. Find the total painted surface area.
Total surface area
答案
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