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# Geometric Series with Complex Number watch

1. A series is defined by C and S below:

The question is asking me to find expressions for both C and S, and I have no idea what to do. It is question 2)b)ii) on the link below:
http://www.mei.org.uk/files/papers/fp208ja_lsgz.pdf

Thanks
Sora
2. (Original post by Sora)
A series is defined by C and S below:

The question is asking me to find expressions for both C and S, and I have no idea what to do. It is question 2)b)ii) on the link below:
http://www.mei.org.uk/files/papers/fp208ja_lsgz.pdf

Thanks
Sora
Consider summing and grouping them together - see Exercise 3G for more detail
3. (Original post by Sora)
A series is defined by C and S below:

The question is asking me to find expressions for both C and S, and I have no idea what to do. It is question 2)b)ii) on the link below:
http://www.mei.org.uk/files/papers/fp208ja_lsgz.pdf

Thanks
Sora
Write the expressionin this way.
4. (Original post by Dualcore)
Write the expressionin this way.
Okay, I did this. What next?
5. (Original post by Sora)
Okay, I did this. What next?
Find the thing you have to times each term by to get to the next term, then use the geometric series formula for series.
6. (Original post by Dualcore)
Find the thing you have to times each term by to get to the next term, then use the geometric series formula for series.
I think I have that too, but I am still unsure of where to go
7. (Original post by Sora)
I think I have that too, but I am still unsure of where to go
Post what you have .
8. (Original post by Dualcore)
Post what you have .

From this we get the common ratio as:

9. (Original post by Sora)

From this we get the common ratio as:

What's the first term? What's the equation for summing geometric series from term 1 to term n?
10. (Original post by Sora)

From this we get the common ratio as:

Have you got an expression for the sum of all the terms using the formula?
11. (Original post by Sora)
Okay, I did this. What next?
You've written

Then write down
Add them together and divide by 2. You will get C
Subtract the 2nd from the 1st and divide by 2. You will get S
Hint:

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