Infinite Sum of a Sequence.

My Code:

syms k x

y= 1-8*(-0.4)^(k)+7*(0.4472135955)^(k)*(cos(2.0344439358*k)-sin(2.0344439358*k))

E=symsum((y-1)^2,k,0,inf)

Im getting this:

>> Untitled

y = 7*(8056283928195279/18014398509481984)^k*(cos((4581160475587523*k)/2251799813685248) - sin((4581160475587523*k)/2251799813685248)) - 8*(-2/5)^k + 1

E = symsum((7*(8056283928195279/18014398509481984)^k*(cos((4581160475587523*k)/2251799813685248) - sin((4581160475587523*k)/2251799813685248)) - 8*(-2/5)^k)^2, k, 0, Inf)

Why am I not getting a sum?

Answer 1

[Birdman]

Change

E=symsum((y-1)^2,k,0,inf)

to

E=vpa(symsum((y-1)^2,k,0,inf))

[Hussein Badran]

Thank you so much!