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WJEC C4 17th June 2016

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Goodbye, A*. :sigh:
Reply 81
Avatar for nh98
nh98
1
Original post by 98matt
The volume of revolution involved two trig equations. You had to spot that:
sin²x+cos²x = 1 (very easy)

sinxcosx + sinxcosx = sin2x (double angle formula thing)

then a simple integration to get 3.73


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ok so i was really stupid and didn't spot that sin^2x + cos^2x = 1, used the whole rearranged double angle formula to integrate, and then integrated sin2x but i did get 3.73, so i just did it the really long way around, would i still get the 6 marks?
Reply 82
Avatar for Dominae
Dominae
6
Can someone quote me when there is an unofficial mark scheme? Thanks :smile:
Original post by nh98
ok so i was really stupid and didn't spot that sin^2x + cos^2x = 1, used the whole rearranged double angle formula to integrate, and then integrated sin2x but i did get 3.73, so i just did it the really long way around, would i still get the 6 marks?


You probably would. It's still a correct method, and that gets you the marks unless it contradicts explicit instructions in the question.
Reply 84
Avatar for 98matt
98matt
13
Original post by Mango88
I integrated sin2x to get -cos2x/2, is that right?


Yes that's correct. Did you remember to integrate "1" into "x" also? If so, then you must've mistyped the numbers on your calculator - most likely 5/6 marks :smile:

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Reply 85
Avatar for Mango88
Mango88
2
Original post by 98matt
Yes that's correct. Did you remember to integrate "1" into "x" also? If so, then you must've mistyped the numbers on your calculator - most likely 5/6 marks :smile:

Posted from TSR Mobile


Yeah i did!! That's not too bad then, thank you!
Reply 86
Avatar for Dominae
Dominae
6
Original post by nh98
ok so i was really stupid and didn't spot that sin^2x + cos^2x = 1, used the whole rearranged double angle formula to integrate, and then integrated sin2x but i did get 3.73, so i just did it the really long way around, would i still get the 6 marks?


Glad I'm not the only one did this. I was happy when others got the same answer 3.73 but when people started mentioning sin^2x + cos^2x = 1, I was thinking I just got really lucky.

Did you get 1/2 + 1/2 somewhere in your integral to get the 1? I think I remember doing that.
Original post by Dominae
Can someone quote me when there is an unofficial mark scheme? Thanks :smile:


@Dominae It's up on mathemateg
Original post by EJRicketts
@Dominae It's up on mathemateg

How do you access it?
Reply 89
Avatar for Dominae
Dominae
6
Original post by EJRicketts
@Dominae It's up on mathemateg


I can't access it aha :tongue:

Didn't think anybody without an account for the website could either :s-smilie:
Original post by Dominae
Glad I'm not the only one did this. I was happy when others got the same answer 3.73 but when people started mentioning sin^2x + cos^2x = 1, I was thinking I just got really lucky.

Did you get 1/2 + 1/2 somewhere in your integral to get the 1? I think I remember doing that.


It's because you did the Q completely mechanically without thinking lol.
What you did is immediately when you saw cos^2x and sin^2x you converted into
(1±cosx)/2 and then went from there... still right and still all the marks though.
Reply 91
Avatar for Dominae
Dominae
6
Original post by IrrationalRoot
It's because you did the Q completely mechanically without thinking lol.
What you did is immediately when you saw cos^2x and sin^2x you converted into
(1±cosx)/2 and then went from there... still right and still all the marks though.


I have the tendency to do that. :tongue:

But hey, as long as you get the marks right. :colondollar:
(edited 7 years ago)
Original post by Hopefulmedicesty
How do you access it?


Original post by Dominae
I can't access it aha :tongue:

Didn't think anybody without an account for the website could either :s-smilie:


To access it just make an account and then you have to enrol onto the course, so C4. Use their twitter for the link to the file, make sure you translate as you go along through your browser haha
Reply 93
Avatar for Dominae
Dominae
6
Original post by EJRicketts
To access it just make an account and then you have to enrol onto the course, so C4. Use their twitter for the link to the file, make sure you translate as you go along through your browser haha


Somebody just posted a drop box for it on the other thread. I didn't realise anyone could make an account on the site, I thought it was only for students at a specific school :ahee: Where were you for the C3 exam!? :wink:


Also, let's take a moment to appreciate the fact that maths is the same in every language, cause I can't speak/read Welsh for ****.
Original post by EJRicketts
To access it just make an account and then you have to enrol onto the course, so C4. Use their twitter for the link to the file, make sure you translate as you go along through your browser haha


Thank you !!!!!!!!
Reply 95
Avatar for Dominae
Dominae
6
Original post by Hydeman
Goodbye, A*. :sigh:


:hugs:
Reply 96
Avatar for Jack1066
Jack1066
OP
17
Mark Scheme: https://www.dropbox.com/s/is5d0l1smt7d5d3/C4%20Mark%20Scheme%202016.pdf?dl=0

Question Paper: https://www.dropbox.com/s/h4wwqjjja79fhb4/C4%20Summer%202016%20QUESTION%20PAPER.pdf?dl=0
Reply 97
Avatar for Dominae
Dominae
6
Buggered up trig somehow cause I'm a simpleton, might have cost me a B grade in this paper but oh well :tongue:

Reckon I got 47 marks, hopefully which is a C
Reply 98
Avatar for Dominae
Dominae
6
I will wet myself if I found out I have done better in C4 than C3
Original post by Jack1066


I think this unofficial mark scheme is wrong in one question. They have k/25 being greater than 1. But the maximum value of cosx is 1. So k/25 should be less than or equal to one and greater than or equal to -1. Am I a total idiot or am I right?

EDIT: No I get it now, I misread the question, my bad. It says no solutions, not solutions. That's a mark lost probably.
(edited 7 years ago)

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