complex sequence help (1 Viewer)

[lqmoney]

The question is from 2020 NSBHS 4U Trial. The first part was not difficult to get out, but I do not understand how to get ii. The second image is the answer I found in the same document on THSC, but I do not understand how they got from the second last to the last line, and I am not convinced the limit even exists?

 

[WeiWeiMan]

View attachment 43653View attachment 43654
The question is from 2020 NSBHS 4U Trial. The first part was not difficult to get out, but I do not understand how to get ii. The second image is the answer I found in the same document on THSC, but I do not understand how they got from the second last to the last line, and I am not convinced the limit even exists?

i'm pretty sure it's wrong (I hope it's wrong at least)

 

[liamkk112]

View attachment 43653View attachment 43654
The question is from 2020 NSBHS 4U Trial. The first part was not difficult to get out, but I do not understand how to get ii. The second image is the answer I found in the same document on THSC, but I do not understand how they got from the second last to the last line, and I am not convinced the limit even exists?

yeah pretty sure the limit won’t exist, because of the i in the exponent it’s really a limit of cosines and sines (potentially it could converge to 1, but i really doubt it at first glance)