Trigonometry - Cosec summation

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Homework Help Overview

The discussion revolves around the summation of cosecant functions, specifically the expression $$\csc\frac{\pi}{32}+\csc\frac{\pi}{16}+\csc\frac{\pi}{8}+\csc\frac{\pi}{4}+\csc\frac{\pi}{2}$$ and its relation to the cotangent function, expressed as ##\cot\frac{\pi}{A}##. Participants are exploring how to simplify or evaluate this expression in the context of trigonometry.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants discuss writing cosecant in terms of sine and attempting to find a common denominator, but express frustration at the lack of progress. There are suggestions to explore relationships between cotangent functions and the cosecant series, with one participant noting the potential for telescoping series.

Discussion Status

Some participants have offered insights into potential relationships between cotangent and cosecant, suggesting that expressing each cosecant as a difference of cotangents might facilitate summation. There is a recognition of the complexity of the problem, with varying levels of understanding and attempts to clarify the approach.

Contextual Notes

There is a noted typo in one of the posts regarding the angles involved, which may affect the interpretation of the problem. Additionally, the presence of repeated terms in the summation is acknowledged, which could influence the approach taken by participants.

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Homework Statement


If
$$\csc\frac{\pi}{32}+\csc\frac{\pi}{16}+\csc\frac{\pi}{8}+\csc\frac{\pi}{4}+\csc\frac{\pi}{2}$$
has the value equal to ##\cot\frac{\pi}{A}## then find A.
A)61
B)62
C)63
D)64

Homework Equations


The Attempt at a Solution


Writing cosec in terms of sin and taking the LCM to make a common denominator doesn't seem to be of any help.

I can find the value of each term but that would be tedious and of no use.

I honestly cannot figure out how should I proceed here.

Any help is appreciated. Thanks!
 
Last edited:
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Pranav-Arora said:

Homework Statement


If
$$\csc\frac{\pi}{32}+\csc\frac{\pi}{16}+\csc\frac{\pi}{2}+\csc\frac{\pi}{4}+\csc\frac{\pi}{2}$$
has the value equal to ##\cot\frac{\pi}{A}## then find A.
A)61
B)62
C)63
D)64


Homework Equations





The Attempt at a Solution


Writing cosec in terms of sin and taking the LCM to make a common denominator doesn't seem to be of any help.

I can find the value of each term but that would be tedious and of no use.

I honestly cannot figure out how should I proceed here.

Any help is appreciated. Thanks!

Try showing cot(x)-cot(2x)=csc(2x).
 
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##\csc(\frac{\pi}{2})## appears twice.
All the angles are successive doublings of ##\pi/32##
 
Dick said:
Try showing cot(x)-cot(2x)=csc(2x).

Wow! Thanks a lot Dick! :smile:

How did you come up with that?

Simon Bridge said:
##\csc(\frac{\pi}{2})## appears twice.
All the angles are successive doublings of ##\pi/32##
Very sorry for the typo, its ##\pi/8## instead of the second ##\pi/2##.
 
Pranav-Arora said:
Wow! Thanks a lot Dick! :smile:

How did you come up with that?

I guessed the series must telescope somehow. So somehow cot(2x) must be related to cot(x) with the difference related to a csc. Seems obvious in retrospect, yes?
 
Last edited:
Dick said:
Seems obvious in retrospect, yes?

Yes. I liked the way you came up with cot(x)-cot(2x) and solved the problem in few seconds where I was stuck for a week.

Thank you again! :)
 
Pranav-Arora said:
Yes. I liked the way you came up with cot(x)-cot(2x) and solved the problem in few seconds where I was stuck for a week.

Thank you again! :)

You're welcome, but it took me more than a "few seconds". Still keeping that strategy in mind might help in the future. If you've got the sum of a bunch of csc's equaling a cot, then if you can express each csc as a difference of two cot's you might be able to sum the series easily. Substitute any other functions you want for 'csc' and 'cot'.
 
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Likes   Reactions: 1 person

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