Year 12s: what will be the first way you research your future options? >>

c4

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/AQA-MPC4-QP-JAN13.PDF
MS:
http://filestore.aqa.org.uk/subjects/AQA-MPC4-W-MS-JAN13.PDF

When cotx = 0.

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.

Reply 3

TSR George

Original post by SeanFM

When cotx = 0.

But tanx=1/0 isn't possible?

Reply 4

Kevin De Bruyne

If you write cotx in terms of its components, then..

Reply 5

TSR George

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

Correct.

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