MATLAB: Infinite Sum of a Sequence.

sum

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?

Best Answer

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