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# C3: Trigonometry

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1. Hi,

I have been asked to find . However, I'm not sure how to work this out.
I have been given the formulae and . My teacher said that the latter is not always true, if that's any help. So what I did was: , and put that into my calculator (in radians mode), but it gave me 1.32, which is wrong as the answer is -1.

Where am I going wrong here? Any help is appreciated!
2. (Original post by Prestoria)
Hi,

I have been asked to find . However, I'm not sure how to work this out.
I have been given the formulae and . My teacher said that the latter is not always true, if that's any help. So what I did was: , and put that into my calculator (in radians mode), but it gave me 1.32, which is wrong as the answer is -1.

Where am I going wrong here? Any help is appreciated!

And when tanx = 0
3. Your teacher is wrong for a start, the definition of cot(x) is 1/tan(x).
Basically if you re-write your question as 1/tan(3PI/4), which if you do on a calculator would give 1/(-1) which will give you the answer of -1.
4. I assume both way works - at least if tan doesn't equal 0. Thanks to the both of you, I really appreciate your speedy responses.
Your teacher is wrong for a start, the definition of cot(x) is 1/tan(x).
No. The teacher is not wrong. Your definition is incomplete

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