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# Trig Identities Core 3 watch

1. Hey
Please can someone help me with this question...
'Solve this equation, giving all values of x to the nearest degree in the interval 0< x <360'

cosec^2x + cotx - 2 = 0 '

i have started the question but cannot finish it because it doesn't appear to work. I did..

1 + cot^2 x + cotx - 2 = 0
cot^2 x = cotx -1 = 0 however this will not factorise!!
2. So what if it doesn't factorise?
3. Easy if it won't factorise complete the square or use the formula.

Sorry that came across as a tad condecending but, C3 is a calculator paper so there may be some quadratics that wont factorsie nicely, that shouldn't be an issue though because you can deal with that with the calculator.
4. you got to cot^2 (x) + cot (x) +1 fine.

Then I would replace cot (x) with t.

Let cot (x) = t

t^2 + t +1 = 0

cot of most angles is a fraction, which is why you can't factorise it.

I would use the quadractic formaula to solve the equation for t and then say cot (x) = t

so inverse cot (t) will give you the angle.

5. Oh thankkss
i'll try that now... i just thought that i must have gone wrong somewhere if it involves the quadratic formula.
but i'll have a go.
6. on C3, if it doesn't involve the quadratic formula, you're either VERY lucky...or wrong!
7. (Original post by louisa17)
on C3, if it doesn't involve the quadratic formula, you're either VERY lucky...or wrong!
That's definitely not true... I'd say that most (exam) questions of this nature actually don't use it. For example, produces something that you can factorise easily.

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Updated: September 29, 2010
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