Edexcel C3,C4 June 2013 Thread

Stuck on this, any help is appreciated! Stuck on the whole question!

Stuck on this, any help is appreciated! Stuck on the whole question!

Actually, after subbing in values, I think they may actually be equivalent. But I'm not sure how to justify it.

I'm not sure if you can just square root both sides like you did though, you need to account for negative roots as well.

Anyone doing Solomon/Elmwood papers?

I had to get an A* in maths or further maths (aced C4 in January) and they helped a lot.

i've done all C3 soloman papers, should i then do the elmwood papers for C3? or do actually past papers, cuz exam is this thursday? thanks

hey guys, I am quite confused about the edexcel c3 june 2006 q5a, and here is how I worl the question, am I correct?

i am confused about the cancelling of cos^2 (2K), why can it be eliminated?
my teacher told me that
if x^2 = 2x , I cannot cross out anything but putting the 2x on the same side as x^2 and carry on working.
why in the q5, the cos^2 (2k) can be eliminated? will this cause a loss of answer?
in what situation can a quantity be eliminated?

thank you soooo much!! please help!

which paper is this? just so i can check if i the got right answer

For part (a), use the identity in the question and the fact that $cos3x=cos(2x+x)$.

For part (b), try expressing the two fractions as a single fraction.

So if I left my answer as $\dfrac{16x^2}{(x^2-1)^2}=\dfrac{(y^2-1)^2}{y^2}$, would that probably be okay?

Erm.. well.. you're multiplying through by cos^2 2k , so where you've got your 5th line, you multiply through by cos^2 2k , and now you'll have 2(2k-1) + 2sin2kcos2k=0.. so on your 6th line you shouldn't have cos^2 2k at the bottom. and where you thought you cancelled off, you're meant to use sin2A=2sinAcosA formula. So 2sin2kcos2k = sin4k... and that's how you get the sin4k from the equation. everything else you did is correct. Hope this helped

on my 5th line, i am actually putting two fractions into one, since the bottom of the middle fraction is cos2k, i multiply it bu another cos2k in order for it to be combined into one fraction (which i think it is a normal practice), am i wrong for doing this ? can you explain ??

thank you !!!!!

Anyone know if proof by contradiction will ever actually come up?

I know how to draw it but Im useto using the cast diagram and that seems to be pretty useless atm.

C4: How do you integrate cot2x? Formula book states that the integral of cotx is ln|sinx| so would it be... 0.5ln|sin2x|?

Try using the substituion let u = 2x