Given that the first term A1 of sequence an = radical 2, a (n + 1) = radical (2 + an), find the general term formula of sequence an The teacher's teaching method is to assume that an = 2cos (θ n) θ n ∈ (0,90 °) So, 2cos θ (n + 1) = radical (2 + 2cos (θ n)) = 2cos (θ n / 2) is obviously wrong... Isn't the half angle formula like this? In this case, we can't go on... What's wrong with this idea? How can we go on with this idea?

Given that the first term A1 of sequence an = radical 2, a (n + 1) = radical (2 + an), find the general term formula of sequence an The teacher's teaching method is to assume that an = 2cos (θ n) θ n ∈ (0,90 °) So, 2cos θ (n + 1) = radical (2 + 2cos (θ n)) = 2cos (θ n / 2) is obviously wrong... Isn't the half angle formula like this? In this case, we can't go on... What's wrong with this idea? How can we go on with this idea?

Try the previous several, an is monotonically increasing, and the function COS is decreasing in the interval (0,90 °), so this assumption must be wrong. I think that θ n is multiplication. It turns out that the suffix 2cos θ (n + 1) = root (2 + 2cos (θ n)) = 2cos (θ n / 2) is correct, so θ (n + 1) = θ n / 2, etc

The general term formula of the number sequence in senior one mathematics
Given that the sum of the first n terms of the sequence {an} is Sn, and ㏒ (Sn + 1) = n + 1, find the general term formula

log(Sn+1) =n+1
Sn +1 = 10^(n+1) (1)
n=1,
a1+1=100
a1=99
S(n-1) +1 = 10^n (2)
(1)-(2)
an = 9.10^n
ie
an =99 ; n=1
=9.10^n ; n=2,3,4,...

The subset of set {- 1,2,3,1} has___ The subset of set {(- 1,2), (3,1)} has___

Are there subsets or subsets