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# C3 Trigonometry Help watch

1. Hi,
I came across this question:
cot135 degrees - find the exact value.
However, I noticed that in the answer's that they just simply found what the sign was and didn't actually use the triangle method to find the surd form. I was just wondering how I would approach these sorts of questions and If I would have to use the triangle method, then how would I go about doing it?
2. (Original post by rose1234)
Hi,
I came across this question:
cot135 degrees - find the exact value.
However, I noticed that in the answer's that they just simply found what the sign was and didn't actually use the triangle method to find the surd form. I was just wondering how I would approach these sorts of questions and If I would have to use the triangle method, then how would I go about doing it?
remember that cot = cos/sin
that sin(180-x) = sin(x)
and that cos(90-x)=-cos(90+x)

No triangles needed - just trig rules (these ones are easy to remember from graphs, and you need to remember a couple of fixed values of sin and/or cos too)
3. It's easiest to just consider the graph of cot x. It's a standard angle as is cot(45) and when .
4. Keeping in mind that:

1) ,

2) has a periodicity of (where , where is an integer),

,
as .

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Updated: September 4, 2016
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