The Student Room Group

Intergration of Trig

Scroll to see replies

Original post by Dopey'
Thanks again :smile:


You are welcome.
Reply 41
Original post by Mr M
You are welcome.


Mr M can you please quickly explain why -ln(e+1) + ln2 = -ln(e+1)/2)
and not ln(2/(e+1)) ?
Original post by Dopey'
Mr M can you please quickly explain why -ln(e+1) + ln2 = -ln(e+1)/2)
and not ln(2/(e+1)) ?


They are the same.

lnab=lnba\displaystyle \ln \frac{a}{b}=-\ln \frac{b}{a}

Use your knowledge of the laws of logarithms to figure out why.
Original post by Dopey'
Mr M can you please quickly explain why -ln(e+1) + ln2 = -ln((e+1)/2)
and not ln(2/(e+1)) ?


They are the same thing
Reply 44
Original post by Mr M
They are the same.

lnab=lnba\displaystyle \ln \frac{a}{b}=-\ln \frac{b}{a}

Use your knowledge of the laws of logarithms to figure out why.


Thanks, Im really struggling with permutations and combinations.
For example this question

In how many ways can a committee of four men and four women be seated in a row if
a) they can sit in any positions - which is 8!
b) no one is seated next to a person of the same sex? < I dont get this?
Original post by Dopey'
Thanks, Im really struggling with permutations and combinations.
For example this question

In how many ways can a committee of four men and four women be seated in a row if
a) they can sit in any positions - which is 8!
b) no one is seated next to a person of the same sex? < I dont get this?


Think of it as 4 double seats containing MF instead of 8 single seats.

Don't keep adding to this thread - if you have new questions about a different topic make a new thread.
Reply 46
Original post by Mr M
Think of it as 4 double seats containing MF instead of 8 single seats.

Don't keep adding to this thread - if you have new questions about a different topic make a new thread.


Will do, can you please help me finish this and I will create a new thread from now on :smile:

so 4! = 24 options theres something missing, this is a hard topic :frown:
Original post by Dopey'
Will do, can you please help me finish this and I will create a new thread from now on :smile:

so 4! = 24 options theres something missing, this is a hard topic :frown:


Well at the moment you have every man paired with a particular woman ...
Reply 48
Original post by Mr M
Well at the moment you have every man paired with a particular woman ...


I was moving the figures around and I got the right answer but it doesnt apply to any other questions so I think on the off chance its right lol

I did

4! x (4! x 2!) = 1152
Original post by Dopey'
I was moving the figures around and I got the right answer but it doesnt apply to any other questions so I think on the off chance its right lol

I did

4! x (4! x 2!) = 1152


So you have 4! ways to arrange the double seats

But there are 4! male/female pairings

And the rows can be populated in 2 different ways

MF MF MF MF or FM FM FM FM
Reply 50
Original post by Mr M
So you have 4! ways to arrange the double seats

But there are 4! male/female pairings

And the rows can be populated in 2 different ways

MF MF MF MF or FM FM FM FM


Are you saying the Calculation above it right?

So for this question ill go through your step
six people are going to travel in a six-seater minibus but only 3 of them can drive. In how many different ways can they seat themselves?

So If i treat the people who can drive as one

D CCC

D= Drive C= Cant drive

4! ways to arrange the seats
but there are 3 in who can drive so 3!
and the seats can be populated in 2!

so 4! x (6! x 2!) I dont get this at all
(edited 11 years ago)
Original post by Dopey'
Are you saying the Calculation above it right?

So for this question ill go through your step
six people are going to travel in a six-seater minibus but only 3 of them can drive. In how many different ways can they seat themselves?

So If i treat the people who can drive as one

D CCC

D= Drive C= Cant drive

4! ways to arrange the seats
but there are 3 in who can drive so 3!
and the seats can be populated in 2!

so 4! x (6! x 2!) I dont get this at all


That is very wrong. The other two people who are capable of driving can sit in any of the passenger seats.

How many ways to do it are there if only 1 person of the 6 can drive?
Reply 52
Original post by Mr M
That is very wrong. The other two people who are capable of driving can sit in any of the passenger seats.

How many ways to do it are there if only 1 person of the 6 can drive?


5! who cant drive = 120 options
Original post by Dopey'
5! who cant drive = 120 options


But 3 people can drive so what is the answer ...
Reply 54
Original post by Mr M
But 3 people can drive so what is the answer ...


5! x 3 = 360 which is the answer but Ill look at another question and I cant understand how to apply the method

Quick Reply

Latest