AS Exexcel Maths C2 help !!!

Hello, i thought this was a good oppertunity to ask for help on revision before the C2 exam next monday :smile:

First question: Geometric sequences..

Q: Find the sum of the following series: 1024 - 542 + 256 - 128 + ... + 1

A: a=1024
r= -542/1024 = -1/2
and nth term =1

1024 (-1/2) (power n-1) = 1

Then it changes to: (-2) (power n-1) = 1024

the question is i don't know how they got to this step (its the example on page 101 in the green textbook)

help me! x

Reply 1

DreamsComeTrue.

OP

1

Another Question on the June 2005 past paper
Q 5.

The circle C with the centre at the point A, has the equation:
x (squared) + y (squared) - 10x + 9 = 0

a) how do you find the centre?
b) How do we find the radius?

Reply 2

Muppety_Kid

17

DreamsComeTrue.

Hello, i thought this was a good oppertunity to ask for help on revision before the C2 exam next monday :smile:

First question: Geometric sequences..

Q: Find the sum of the following series: 1024 - 542 + 256 - 128 + ... + 1

A: a=1024
r= -542/1024 = -1/2
and nth term =1

1024 (-1/2) (power n-1) = 1

Then it changes to: (-2) (power n-1) = 1024

the question is i don't know how they got to this step (its the example on page 101 in the green textbook)

help me! x

Look at the yellow explanation bubbles. They've divided by 1024 and taken the reciprocal, I think :s-smilie:

Hope this helps

Reply 3

figureeight

11

DreamsComeTrue.

Another Question on the June 2005 past paper
Q 5.

The circle C with the centre at the point A, has the equation:
x (squared) + y (squared) - 10x + 9 = 0

a) how do you find the centre?
b) How do we find the radius?

For an equation:

x^2 + y^2 + 2fx + 2gy +c = 0

Then the centre is at

(-f,-g)

and the radius is

\sqrt{f^2 + g^2 - c}

Reply 4

Muppety_Kid

17

DreamsComeTrue.

Another Question on the June 2005 past paper
Q 5.

The circle C with the centre at the point A, has the equation:
x (squared) + y (squared) - 10x + 9 = 0

a) how do you find the centre?
b) How do we find the radius?

Tch, you should know this from Chapter 4 :p:

Only joking, look at the rule on page 60.

(x-a)^2+(y-b)^2=r^2

is the eq. of a circle, where (a,b) is the centre and r is the radius.

You need to rearrange the equation to get it into that form.

I'll have a look later (have to go now), but quote me if you get stuck.

Reply 5

Adjective

12

Complete the square for the terms in x and the terms in y respectively. That'll give you

(x-a)^2 + (y-b)^2 = r^2

.

You should be able to see the centre and the radius from that.

Reply 6

DreamsComeTrue.

OP

1

Adje

Complete the square for the terms in x and the terms in y respectively. That'll give you

(x-a)^2 + (y-b)^2 = r^2

.

You should be able to see the centre and the radius from that.

thanks! i thought it had something to do with completing the sqaure... great.. one of those things i'm so bad at!! lol :s-smilie:

So if i started to complete the square, i'd get..

(x-5)^2 - 25+9 + (y-0)^2 = 0

(x-5)^2 - 16 + (y-0)^2 = 0

(x-5)^2 + (y-0)^2 = 16

Yey! so centre is (5,0) and Radius is 4?

thanks! that saved my life!! :smile:

Reply 7

DreamsComeTrue.

OP

1

Another question on the June 2005 Paper please:

question 10: b)
here is my differentiated thing : 2 + 16^-3

the Question is: use calculas to show that y is increasing for x (is bigger than 2).

What x value do we sub in?

Reply 8

DreamsComeTrue.

OP

1

June 2005 Question 2 b)

Where do we go from

log (x+1)/x = log 7 ?

Reply 9

nicangeli

(x + 1 ) / x = 7

since they are the same base.

1 = 6x

x = 1/6

Reply 10

DreamsComeTrue.

OP

1

nicangeli

(x + 1 ) / x = 7

since they are the same base.

1 = 6x

x = 1/6

Hey thanks :smile:

its quite simple really lol

Reply 11

The Salty Dog

Just did the June 2005 paper this morning. Got 56%. This is my 2nd retake of C2 (don't ask about the first one :P) after getting a pretty crap mark in the first place. I figured I might as well sit again, I've got nothing to lose.

Yeah so on that June 2005 paper, the logs question is as nicangeli pointed out. You just have to use rules of logs to make (x+1) over x, and then the logs can cancel out, giving x = 1/6.

The circles question caught me out: I didn't notice that there wasn't any y value on the 9, but that was in fact the constant. (Don't jump me on this vocabulary people!)

The question that got me was Q10: I don't really understand how you integrate 8/x^2. The mark scheme has it over -1 after integration?

Reply 12

DomAD

9

The Salty Dog

The question that got me was Q10: I don't really understand how you integrate 8/x^2. The mark scheme has it over -1 after integration?

Unparseable latex formula:

$\int\frac{8}{x^2} $

is equal to

Unparseable latex formula:

$ \int8x^{-2} $

. Integrating this gives you

Unparseable latex formula:

$ [\frac{8x^{-1}}{-1}+k] $

which simplfies to

Unparseable latex formula:

$[-8x^{-1}+k] $

or

Unparseable latex formula:

$ [\frac{-1}{8x}+k] $

Reply 13

The Salty Dog

Ahh I see now. Nice one.

Reply 14

DreamsComeTrue.

OP

1

Can i ask how people write their maths expressions out like that cos it will make life a lot less confusing

Reply 15

DreamsComeTrue.

OP

1

Some help please on the May 2007 paper, question one.

evaluate to boundaries 8 and 0: 1/(x)^-1/2

In english: 1 over root x.
Please eplain the next step, they do have it in the answer booklet but i've been thinking on it for ages and have no idea how it got there!!!!

Reply 16

DreamsComeTrue.

OP

1

Another Question on the sine rule.

in the green text book at the bottom of page 23 question 2a)
i found the first set of x and y values
i found the second x value (180- first x value)
but i can't find the second y value!!!

help.

Reply 17

ClaireHogben

13

^^ write out the question and i might be able to help!

Reply 18

DreamsComeTrue.

OP

1

ClaireHogben

^^ write out the question and i might be able to help!

I'll try:

In triange ABC, AC= 12cm, AB= 8cm, Angle ACB= 40 degrees.

the question is find the two sets of values for CAB and CBA.

The first set i got right: 74.6 degrees and 64.4 degrees.
Second values i got right: 105.4 degrees (CBA) and the problem is what is CAB??
:smile:

Reply 19

ClaireHogben

13

what is CAB? you mean angle A (between lines b and c)??

i dont think im following you..... sorry

AS Exexcel Maths C2 help !!!

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