第2个回答 2015-01-13
对数螺线 r=e^θ, 则 r^2=e^(2θ)
在 θ=π 的邻域内, θ = π+arctan(y/x) ,
故得直角坐标方程 x^2+y^2 = e^[2π+2arctan(y/x)] = e^(2π)e^[2arctan(y/x)]
两边对 x 求导数, 得 x+yy' = e^(2π) e^[2arctan(y/x)] [(xy'-y)/(x^2+y^2)]
θ=π 时, y = 0, x = -e^π, 代入上式,得
- e^π = e^(2π) e^0 (-y'/e^π) = - e^π* y',
则切线斜率 k = y‘(-e^π) = 1
切线方程 y=x+e^π本回答被提问者和网友采纳