y=x^(3⼀2)在[0,1]上长度计算过程

2025-05-16 06:01:20
推荐回答(2个)
回答1:

y`=[x^(3/2)]`=3√x /2
代入弧长公式,
得 s=∫<0,1>√(1+y`²)dx
=∫<0,1>√(1+9x/4)dx
=(4/9)(1+9x/4)^(3/2)|<0,1>
=(4/9)(13/4)^(3/2)-4/9

回答2:

dy = (3/2)x^(1/2) dx
dl = √{(dy)²+(dx)²} = √{(9x/4)+1}dx
l = (0至1)∫√{(9/4)x+1}dx
= 2/{3*9/4) √ {(9x/4)+1}³ ||(0至1)
= (8/27) * √ {(9x/4)+1}³ ||(0至1)
= (8/27) * { √[(9/4)+1]³ - √[0+1]³ }
= (8/27) * { √[13/4]³ - 1 }
= (8/27) * { 13√13/8 - 1 }
= (13√13 - 8 ) / 27