作业帮 > 综合 > 作业

高数微积分题一道The base of a circular fence with radius 10 m is giv

来源:学生作业帮 编辑:作业帮 分类:综合作业 时间:2024/05/17 00:15:44
高数微积分题一道
The base of a circular fence with radius 10 m is given by x = 10 cos t; y = 10 sin t.The
height of the fence varies from 3 m to 5 m such that,at position (x,y),the height is given by
the function h(x,y) = 4 + 0.01(x2 -y2).Suppose that 1 litre of paint covers 100 m2.Sketch
the fence and determine how much paint you will need if you paint both sides of the fence.
Ans:5 litre
请具体讲一下思路,万分感激!
如图进行微分.微元面积等于高度h乘以微元弧长.
dS=h*dl=h*R*dθ
所以
S=∫Rhdθ(积分范围从0到2π)
 =∫10*(4 + ((cosθ)^2 -(sinθ)^2))dθ
剩下的你会算了吧