C3 January 2013 25/01/2013

Reply 1860

Commenting94

Original post by posthumus

ln(5+e^2y) - 2y -1 = 0

hmm so what happens now ?

5+e^2y - e^2y- e = 1

4-e=0 :tongue:

HELP !!

ThisExcellency just posted the method ^^

Hope you understand it now :smile:

Reply 1861

TPJY

10

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

Reply 1862

posthumus

20

Original post by TPJY

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

SOMEONE PLEASE CORRECT ME IF I'M WRONG...

I believe you always start of with what is affecting x (inside brackets)
Always do translate & then stretching/ reflecting

if its outside bracket...affecting y

then its other way round... do stretching/reflecting & then translate

Reply 1863

Meme4

1

Original post by TPJY

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

bodmas
multiply first

so for your example, divide x values by 3 then -5

Reply 1864

TOSully

Original post by TPJY

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

You use BIDMAS (or whatever you use to remember it (Brackets, Indicies, Division, Multiplication, Addition and Subtraction)). So in this case of f(x) = 2f(x)+3, you would multiply the y coordinate by 2 first, the add 3 to the answer from that multiplication.

Reply 1865

JJMills

Original post by TPJY

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

In your example it doesn't matter which order you do them in because the -5 is shifting the graph to the right 5 units and the 2 in front of the f(x-5) is stretching the graph vertically by 2.

For 2f(x) + 3 you just need to remember your order of operations so you would multiply the co-ordinates first then add the 3 to them.

Reply 1866

cookie555

Hello how on earth have they solved moments there in the mark scheme? (sorry for mechanics) I remember doing this is physics but never understood it

Original post by TPJY

what do you do if you
get a double transforation affecting the same
thing?

like this: 2f(x)+3
or f(3x+5)

how do you know which order to do them in??? in
the exams so far they have only given one of
each, for example:

2f(x-5)

:

Treat f(x) like any number, x.

To get from x to 2x+3 you had to have multiplied first to get 2x and then added 3 to get 2x+3.

Same for brackets. To get to x to 3x+5, you had to multiply by 3 to get 3x and then added five to get 3x+5.

For 2f(x-5) same thing.

You minused 5 from x and then multiplied the whole thing by 2 to get 2(x-5)

Reply 1868

Mesutozil

what trig equations do we need to know that we won't be given in the exam? I know all AS but i don't memorise cosec and sec equations in relation to sin cos and tan yet

Reply 1869

lanky

If the question does not state how many decimal places or significant figures to answer to, what is the best amount to go for? :confused:

Reply 1870

JJMills

Original post by lanky

If the question does not state how many decimal places or significant figures to answer to, what is the best amount to go for? :confused:

I've never seen a maths exam penalise you for having too many significant figures (unless stated otherwise in the question) however ~3 is usually standard.

Reply 1871

MedMed12

21

Original post by Commenting94

Really sorry I can't rememeber which paper, I done a couple random practice papers and solomons yesterday, It was from one of them.

I don't think its appeared in any of the past papers from 06-12 though. Just a small possibilty it might come up today?

if its a solomon paper then im not too worried hehe
its not in our textbook either :biggrin:

Reply 1872

TOSully

Original post by lanky

If the question does not state how many decimal places or significant figures to answer to, what is the best amount to go for? :confused:

I always give my answers to 3 decimal places and the mark scheme always says they accept a number which rounds to .xyz You may have seen it while you were doing practise exams, it is written in the margin as 'awrt ...'. Say the answer to x = 1.1234567, I would write my answer as x= 1.123 and in the margin of the mark scheme, it will say 'awrt x-1.12'. :smile:

BTW, awrt means 'Anything which rounds to...'

Reply 1873

Tikara

is 2cosec2A the same as 2/sin2A or 1/2sin2A??

Reply 1874

posthumus

20

Original post by lanky

If the question does not state how many decimal places or significant figures to answer to, what is the best amount to go for? :confused:

I havn't seen a question where you get decimal places in your answer and it hasn't stated in the question how many to.

Well anyway I'd suggest 2 or 3 :smile:

no less no more.

Reply 1875

TPJY

10

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

Original post by posthumus

SOMEONE PLEASE CORRECT ME IF I'M WRONG...

I believe you always start of with what is affecting x (inside brackets)
Always do translate & then stretching/ reflecting

if its outside bracket...affecting y

then its other way round... do stretching/reflecting & then translate

Original post by Meme4

bodmas
multiply first

so for your example, divide x values by 3 then -5

you two seem to be contradicting each other :s

Reply 1876

JJMills

Original post by Mesutozil

what trig equations do we need to know that we won't be given in the exam? I know all AS but i don't memorise cosec and sec equations in relation to sin cos and tan yet

sin x / cos x = tan x
sin^2 x + cos^2 x = 1
1 / cos x = sec x
1 / sin x = cosec x
1 / tan x = cot x
sin 2x = 2sinxcosx
cos 2x = cos^2 x - sin^2 x = 1 - 2 sin^2 x = 2 cos^2 x - 1
tan 2x = 2tan x / (1 - tan^2 x)

Reply 1877

Henry.Lister

Someone help please! Question C. I get the wrong answer :/

Original post by TPJY

what do you do if you get a double transforation affecting the same thing?

like this: 2f(x)+3

or f(3x+5)

how do you know which order to do them in??? in the exams so far they have only given one of each, for example:

2f(x-5)
D:

you two seem to be contradicting each other :s

For the first one definitely stretch first then traslate

second one is the other way around

2f(x-5)

doesn't matter which way you do it :smile:

Reply 1879

Dragonrage973

2

Original post by Samira123

No the actual addition formulae?

The proofs of cos(A - B) thing won't come up in the exam. (even though it's just a bit of pythag and working out distances). In the book it says "Although you will not be expected to derive these formulae from first principles, it will help your understanding of them to see how one of them can be derived." :biggrin:

C3 January 2013 25/01/2013

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