- #1

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im stuck on the top question on part B

i can do the difference of 2 squares on the LHS but how do i get rid of the cosec²x

**-**cot²x ??

Thanks

- Thread starter thomas49th
- Start date

- #1

- 655

- 0

im stuck on the top question on part B

i can do the difference of 2 squares on the LHS but how do i get rid of the cosec²x

Thanks

- #2

- 1

- 0

mis-post, oops!

Edit: Well, as I'm here...

[itex]cosec^2\theta - cot^2\theta = 1[/itex]

[itex]cosec^2\theta + cot^2\theta = -1[/itex]

Well, that's the RHS...

[itex]-cot^4\theta = -cot^2\theta \times cot^2\theta\newline[/itex]

[itex]= (1 - cosec^2\theta)(cosec^2\theta - 1)\newline[/itex]

[itex]= -1 + cosec^2\theta - cosec^4\theta - cosec^2\theta\newline[/itex]

Back to the original question!

[itex]cosec^4\theta - cosec^4\theta - 1 = - 1\newline[/itex]

[itex]-1 = -1[/itex]

I think that's correct :S

(Hmm, latex is messed up, how do I make a newline?)

Edit: Well, as I'm here...

[itex]cosec^2\theta - cot^2\theta = 1[/itex]

[itex]cosec^2\theta + cot^2\theta = -1[/itex]

Well, that's the RHS...

[itex]-cot^4\theta = -cot^2\theta \times cot^2\theta\newline[/itex]

[itex]= (1 - cosec^2\theta)(cosec^2\theta - 1)\newline[/itex]

[itex]= -1 + cosec^2\theta - cosec^4\theta - cosec^2\theta\newline[/itex]

Back to the original question!

[itex]cosec^4\theta - cosec^4\theta - 1 = - 1\newline[/itex]

[itex]-1 = -1[/itex]

I think that's correct :S

(Hmm, latex is messed up, how do I make a newline?)

Last edited:

- #3

Gib Z

Homework Helper

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Use the result in part a) like it told you to.

- #4

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3lliot, please do not give out answers. We offer free help here at PF, not free answers.

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