>>435
解答
dy/dx＝-sinx/(1+cosx)

曲線の長さLは、
L＝∫√(1+dy/dx^2)dx
=∫√(2(1+cosx)/(1+cosx)^2)
=∫1/cos(x/2)dx
=∫1/2cos(x/2)(1/(1+sin(x/2))+1/(1-sin(x/2)))dx
=[log((1+sin(x/2))/(1-sin(x/2)))]
=log((1+√2)/(1-√2))=2log(1+√2)
と計算できる