Edexcel A2 C4 Mathematics June 2015 - Official Thread

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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 :biggrin:

okay but what about the tangent parallel to the x axis? then?

Reply 2161

Maham88

Original post by MasonPye

Could someone please post the June 2015 C34 ial mark scheme please!

here are the solutions https://a48aca6bcd82b5ada594d7397b730e907e9902c3.googledrive.com/host/0B1ZiqBksUHNYdUJldmdCUllHZ2M/Edexcel%20C34%20-%20June%202015%20%28IAL%29%20Model%20Answers%20by%20koli248.pdf

Reply 2162

Ripper Phoenix

Original post by TeeEm

numerator zero.

aha okay...

you're a man of very few words :biggrin:

but my teacher said we equate dy/dx to zero if it is parallel to x axis.. is this incorrect?

Reply 2163

Ripper Phoenix

Original post by marco cb

Yep, before I head to school, any last key points to remember in the exam, anyone?

if in doubt, walk out :biggrin:

jk you gotta pass, we all gotta pass!! good luck!!!! :smile:

Reply 2164

TeeEm

Original post by marco cb

Yep, before I head to school, any last key points to remember in the exam, anyone?

iboprufen, imodium, glucose tablets, indigestion tablets, asthma pump (optional), water, tissues, toilet paper, disinfecting gel, ...

Reply 2165

Humbers

Original post by Ripper Phoenix

okay but what about the tangent parallel to the x axis? then?

Parallel to the x-axis means a horizontal line, so no gradient.

therefore the numerator must be equal to zero

Reply 2166

Gilo98

Original post by TeeEm

look at related rates book Q30

Do they have to ask for permission or something? or do they just swap values and rip the Q off you?

Spoiler

Reply 2167

TeeEm

Original post by Ripper Phoenix

aha okay...

you're a man of very few words :biggrin:

but my teacher said we equate dy/dx to zero if it is parallel to x axis.. is this incorrect?

when I was at school (Year 7) we used to chant ...
if a fraction equal zero the only thing that can make it zero is its numerator ...
if a fraction equal zero the only thing that can make it zero is its numerator ...
if a fraction equal zero the only thing that can make it zero is its numerator ...
if a fraction equal zero the only thing that can make it zero is its numerator ...

f4.jpg15.9KB

Reply 2168

Humbers

Original post by Ripper Phoenix

aha okay...

you're a man of very few words :biggrin:

but my teacher said we equate dy/dx to zero if it is parallel to x axis.. is this incorrect?

Yes dy/dx would equal zero

in this case the only way dy/dx can = 0 is if the numerator is equal to zero as you can never divide something to get zero

Reply 2169

manlikem

Original post by asjdj

When you realize you're on your period few hours before the exam.. noooooooooooooooooooooooooooooooooooooooooooo

wtf?

Reply 2170

somevirtualguy

Looks like I got 62/63 marks in C3, if Arsey's right and 64 marks is 90UMS there's still some hope for an A*, here's to hoping :wink:

Reply 2171

marco cb

Original post by Ripper Phoenix

if in doubt, walk out :biggrin:

jk you gotta pass, we all gotta pass!! good luck!!!! :smile:

If I see a tricky ass question 1 that I can't answer, I will most likely have no option but to walk out. But ha thanks - Good luck to you too!

Reply 2172

Ocean3

Can someone explain to me how to reflect a point in a line please?

Reply 2173

marco cb

Original post by TeeEm

iboprufen, imodium, glucose tablets, indigestion tablets, asthma pump (optional), water, tissues, toilet paper, disinfecting gel, ...

Check, check and check.. ran out of toilet paper though,

Reply 2174

TeeEm

Original post by Gilo98

Do they have to ask for permission or something? or do they just swap values and rip the Q off you?

Spoiler

triple rate is the sensible way, although it can be done as a double

Reply 2175

urz13

Does anyone have any tips for sketching vector diagrams to make them easier to understand? Vectors are the one area I just can't seem to get my head round...