# Revision history [back]

age: derivative(abs(xn-a*N/(1-exp(-i*2*pi*k/N)))^2,a)
....:
....:
....:
8*(xn + 8*a/(e^(-1/4*I*pi*k) - 1))/(e^(1/4*I*pi*k) - 1) + 8*(8*a/(e^(1/4*I*pi*k) - 1) + conjugate(xn))/(e^(-1/4*I*pi*k) - 1)

 2 No.2 Revision slelievre 16479 ●19 ●147 ●329 http://carva.org/samue...
age: derivative(abs(xn-a*N/(1-exp(-i*2*pi*k/N)))^2,a)
....:
....:
....:
8*(xn sage: derivative(abs(xn - aN/(1 - exp(-i2pik/N)))^2, a)
8(xn + 8*a/(e^(-1/4*I*pi*k) 8a/(e^(-1/4Ipik) - 1))/(e^(1/4*I*pi*k) 1))/(e^(1/4Ipik) - 1) + 8*(8*a/(e^(1/4*I*pi*k) 8(8a/(e^(1/4Ipik) - 1) + conjugate(xn))/(e^(-1/4*I*pi*k) conjugate(xn))/(e^(-1/4Ipik) - 1)

1)

 3 No.3 Revision slelievre 16479 ●19 ●147 ●329 http://carva.org/samue...

Try this:

sage: derivative(abs(xn - aN/(1 a*N/(1 - exp(-i2pik/N)))^2, exp(-i*2*pi*k/N)))^2, a)
8(xn 8*(xn + 8a/(e^(-1/4Ipik) 8*a/(e^(-1/4*I*pi*k) - 1))/(e^(1/4Ipik) 1))/(e^(1/4*I*pi*k) - 1) + 8(8a/(e^(1/4Ipik) 8*(8*a/(e^(1/4*I*pi*k) - 1) + conjugate(xn))/(e^(-1/4Ipik) conjugate(xn))/(e^(-1/4*I*pi*k) - 1)1)