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# c4

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Why bother with a post grad? Are they even worth it? Have your say! 26-10-2016
1. For Q3b.ii., can someone explain to me why 90* is an answer... (I had 45* and 135*)
QP:
http://filestore.aqa.org.uk/subjects...4-QP-JAN13.PDF
MS:
http://filestore.aqa.org.uk/subjects...W-MS-JAN13.PDF
2. If you divided the equation by cosx (once you converted sin2x into 2sinxcosx) you shouldn't have.
I'm assuming that's what you did.
3. (Original post by pippabethan)
For Q3b.ii., can someone explain to me why 90* is an answer... (I had 45* and 135*)
QP:
http://filestore.aqa.org.uk/subjects...4-QP-JAN13.PDF
MS:
http://filestore.aqa.org.uk/subjects...W-MS-JAN13.PDF
When cotx = 0.
4. (Original post by SeanFM)
When cotx = 0.
But tanx=1/0 isn't possible?
5. (Original post by pippabethan)
But tanx=1/0 isn't possible?
If you write cotx in terms of its components, then..
6. (Original post by SeanFM)
If you write cotx in terms of its components, then..
Oh I see, so you write cotx as cosx over sinx
7. (Original post by pippabethan)
Oh I see, so you write cotx as cosx over sinx
Correct.
8. basically yh

cos x
------- - 2sinx = 0
sinx

then u write sin2x in terms of sinx and cosx using double angle formula

then u should be able to solve by factoring, you would get 0 and 90* as shown in the markscheme but you discard 0 as its not in the range

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