x Turn on thread page Beta
 You are Here: Home >< Maths

# Edexcel A2 C4 Mathematics June 2015 - Official Thread watch

1. (Original post by TeeEm)
here it comes
Any MS or model answers floating sob for this? Thanks
2. (Original post by TeeEm)
what time is the start time for C4 in your school?
13.00 / 13.15 or 13.30?
13:15 or 13:30, depending on the invigilators and any 'issues' they have to face

Posted from TSR Mobile
3. (Original post by TeeEm)
what time is the start time for C4 in your school?
13.00 / 13.15 or 13.30?
13.45 :/
4. 13:45 here.
5. GUYS I Have a small question. In June 13. Q7 Why exactly is it that when the tangent to the curve is parallel to the y axis we equate the denominatior to zero and get y in terms of x and put it in the orig equation? like whats the logic behind that?

also what if it said parallel to the x axis? then what do we do?

6. (Original post by TeeEm)
what time is the start time for C4 in your school?
13.00 / 13.15 or 13.30?
13:30
7. (Original post by Gilo98)
Any MS or model answers floating sob for this? Thanks
I did the C4 questions with my students yesterday but unfortunately I did not retain the answers because it was of no interest.

Tough related rates question ... I wonder who wrote it ...
8. (Original post by kingaaran)
Hopefully - that paper looks really nice, especially the vector question which is surprisingly easy.

Posted from TSR Mobile
Are you referring to the triangle one?
How do you find the exact length of AB?
I got the square root of 61-60arccos(2/3) lol
9. (Original post by Ripper Phoenix)
GUYS I Have a small question. In June 13. Q7 Why exactly is it that when the tangent to the curve is parallel to the y axis we equate the denominatior to zero and get y in terms of x and put it in the orig equation? like whats the logic behind that?

also what if it said parallel to the x axis? then what do we do?

dividing by zero produces infinite gradient
10. (Original post by frozo123)
Are you referring to the triangle one?
How do you find the exact length of AB?
I got the square root of 61-60arccos(2/3) lol
AB= square root of 21
11. (Original post by TeeEm)
I did the C4 questions with my students yesterday but unfortunately I did not retain the answers because it was of no interest.

Tough related rates question ... I wonder who wrote it ...
No worries,would you be able to check my answers?
Spoiler:
Show
you wrote it?
12. (Original post by ridirahman)
AB= square root of 21
how did you do it?
13. (Original post by Ripper Phoenix)
GUYS I Have a small question. In June 13. Q7 Why exactly is it that when the tangent to the curve is parallel to the y axis we equate the denominatior to zero and get y in terms of x and put it in the orig equation? like whats the logic behind that?

also what if it said parallel to the x axis? then what do we do?

If it's parallel to the y-axis, that means the tangent has no gradient - no rate of change of y with respect to x.

Once you have set the differential equal to zero, you have two unknowns and hence you need to use simultaneous equations to solve for those two unknowns. Since that tangent touches a point on that line, the equation you formed by equating your differential equal to zero must satisfy the equation of the line. Hence, you sub it in to work out the x and y.

With regards to your second question, I'm not too sure. If it's parallel to the x-axis, I don't think you can really have a gradient:

.

You'd have a change of y, but the change in x will be 0, and you obviously can't divide by zero, so I think the gradient is undefined - someone will have to confirm that lol :-

Posted from TSR Mobile
14. (Original post by Maham88)
13:30
(Original post by IWantSomeMushu)
13:45 here.
(Original post by ridirahman)
13.45 :/
(Original post by kingaaran)
13:15 or 13:30, depending on the invigilators and any 'issues' they have to face

Posted from TSR Mobile
(Original post by Bustamove)
I think the exam usually starts around 1PM.... if anything, maybe a few minutes late if your school is disorganised...
(Original post by Naga7o)
I start at 2, pretty late compared to other people
(Original post by physicsmaths)
Mine is 2pm

Posted from TSR Mobile
thanks

it looks that it can be between 13.00 and 14.00 with 15 minute gaps
thanks to all...
I am off for my morning walk soon, then do some work, then prepare a C4 poll, then hear people cry ...
Attached Images

15. (Original post by TeeEm)
dividing by zero produces infinite gradient
okay and what if it said parallel to x axis?
16. (Original post by frozo123)
how did you do it?
c^2 = a^2 + b^2 - 2abcos (AOB)

then you subst. a and b like;

25 + 36 - 60(2/3) which gives you 21 so c^2 = 21 = square root of 21

hope this helps
17. (Original post by Ripper Phoenix)
GUYS I Have a small question. In June 13. Q7 Why exactly is it that when the tangent to the curve is parallel to the y axis we equate the denominatior to zero and get y in terms of x and put it in the orig equation? like whats the logic behind that?

also what if it said parallel to the x axis? then what do we do?

Ok so when the tangent is parallel to the Y- axis, it means the tangent is vertical and therefore has an 'infinite' gradient

The expression for dy/dx is -(2x+4y)/(4x+2y) for dy/dx = infinity the denominator must be equal to zero as anything divided by zero is undefined/infinite

so then you get 4x + 2y = 0 y = -2x substitute that into the original equation to solve and get the co-ordinates
18. Yep, before I head to school, any last key points to remember in the exam, anyone?
19. (Original post by ridirahman)
c^2 = a^2 + b^2 - 2abcos (AOB)

then you subst. a and b like;

25 + 36 - 60(2/3) which gives you 21 so c^2 = 21 = square root of 21
of right I was putting cos(2/3) in my calculator lol, thanks
20. (Original post by Gilo98)
No worries,would you be able to check my answers?
Spoiler:
Show
you wrote it?
look at related rates book Q30

TSR Support Team

We have a brilliant team of more than 60 Support Team members looking after discussions on The Student Room, helping to make it a fun, safe and useful place to hang out.

This forum is supported by:
Updated: April 20, 2016
Today on TSR

### How do I turn down a guy in a club?

What should I do?

### My dad said he's stalked me at uni!

Poll
Useful resources

Can you help? Study help unanswered threadsStudy Help rules and posting guidelinesLaTex guide for writing equations on TSR

## Groups associated with this forum:

View associated groups

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE