Edexcel C3,C4 June 2013 Thread

C4 Solomon C question 4- part a (sorry can't seem to upload pictures)

Are supposed to cancel down the direction vector or does it matter if we don't? I've never seen an Edexcel one where we cancel down the direction vector so will it ever come up?

It doesn't matter if you don't,It just changes the value of lambda you get, but you will still end up with the right answer.

C4 Solomon C question 4- part a (sorry can't seem to upload pictures)

Are supposed to cancel down the direction vector or does it matter if we don't? I've never seen an Edexcel one where we cancel down the direction vector so will it ever come up?

Hey guys for iteration (c3) do we have to show working or can we go straight to what x1 is etc. from the calculator?

I got the negative solutions by doibg cast anticlockwise...
I thought you are supposed to since the range has negative part?

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i did cosinverse(3/4) and then put that angle in the negative quadrants in the CAST diagram, where the angle was 41.409... which is the same as cosinverse(-3/4) and putting that in the correct place in the CAST diagram.
so the angle 41.409 should be in the 2nd and 3rd quadrants and u shud get ..
x + 45 = 180 -41.409... ->x = 93.6
x + 45 = 180 + 41.409 .... -> = 176.4
x + 45 =/= -180 + 41.409 since its not in the range.

range was -180 < x<180 ----> -135<x+45<225

you gotta show how to sub in the first value like x1 but the next 2 or 3 you can just right the answers

Also just another quick question do you have to put units? e.g. I was asked to find the rate in a context and hence did so but didn't put units (apply it to the context) does that matter or would I lose a mark despite the maths being correct?

how do you draw something to the power of x ? for example 5^x ?

in the formula booklet of c3

how can e^xlna become a^x?
can someone show me the steps?

thanks a lot!

Anyone able to help me with Part B. I understand that the domain of f^-1(x) is equal to the range of f(x). The mark scheme says the domain is <= 4 however... the range for f(x) cannot equal 4 as x=/=1 and if you were to set your x value as say... -1.5 then your 4-ln(x) would be > 4. Am I mistaken or is the mark scheme incorrect? Thanks in advance

Im hoping for one hard and one easy/normal paper for c3 c4 a paper like c3 june 12 would be so ideal easy 100 ums im startin to get annoyed at one thing obviously you should be prepared as much as possible but it really can be a lottery sometimes when your aiming for 95+ there could be a dificult 2-4 marks in one paper or tricky 2-4 marks thts easy to slip olup on but on another paper its virtually a walk in the park its not fair why exams differ in dificulty why not just make all of the exams difficult these questions on a levels are repetitive this doesnt apply to most ppl on here but for those c-a students its even more of a lottery a easy ppr could mean difference between a or c :/ this applies to all maths papersquite an annoying feat some people will be lucky andvget an easy ride to an a or 90+ grade boundaries dont change much at all aswell i know how theyvwork but i still think its dodgy