I was looking through a solution someone on here posted to a q and I'm not sure I follow...
Can someone pls explain the highlighted step and how you'd go on from there?
(Original post by Horizontal 8)
STEP I question 3
Hence no solutions arise from this.
So we use to find the other angles.
Cosx is -ve for when considering 0<x<2pi
Therefore the angles that we want are:
And this is equal to
STEP I 2003 q
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- 09-06-2012 22:10
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- 09-06-2012 22:19
- 09-06-2012 22:35
hmm I still don't understand why you wouldn't just use the cosx instead of cos(-x) to work through the remainder of the question???
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(Original post by shanban)
- 09-06-2012 22:45
hmm I still don't understand why you wouldn't just use the cosx instead of cos(-x) to work through the remainder of the question???Last edited by z0tx; 10-06-2012 at 01:54.
(Original post by z0tx)
- 09-06-2012 23:17
I think it is because the interval you are dealing with in the equation is . The absolute value gives two possibilities. Since , you rule it out and use the other (positive) value, which is