方程是 x^2/3.5^2+y^2/1.5^2 = 1;y = sqrt(2.25-9/49 x^2);周长C = 4*[积分(0到3.5)∫sqrt(1+(dy/dx)^2)dx] =4*[[积分(0到3.5)∫sqrt(1+(9^2/49^2 x^2)/(2.25-9/49 x^2))dx];这个积分是给不出其原函数的,属于不可积...