For further maths a level, you're allowed to have FP1-3, M1, S2,M2 as part of it, right? So you don't need 3 AS units and 3A2 units ?

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Reply 584

username1259045

17

Original post by Ilovemaths96

sorry still dont understand?

wait sorry, they are using surface area of revolution not arc length

Reply 585

BP_Tranquility

5

Also, the system works to give your maximum grade in maths and further maths, it doesn't try to give max UMS to maths and put the lowest units in further maths, right?

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Reply 586

Ilovemaths96

13

Original post by mmms95

wait sorry, they are using surface area of revolution not arc length

question asks for curved surface area and mark scheme uses arc length formula??

Reply 587

math42

20

Original post by BP_Tranquility

Also, the system works to give your maximum grade in maths and further maths, it doesn't try to give max UMS to maths and put the lowest units in further maths, right?

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Yeah, grade in Maths prioritised before grade in FM before UMS in Maths before UMS in FM

Reply 588

username1259045

17

Original post by Ilovemaths96

question asks for curved surface area and mark scheme uses arc length formula??

you're talking about june 2014 r right? the markscheme is not using arc length, look at the presence of 2pi

Reply 589

username1259045

17

June 2014 ial question 5a
markscheme https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf

qustion paper https://3a14597dd5c7aa2363f067571766...%20Edexcel.pdf

also questions 7a, how to you simplify 720^3/2 x2/9 ???? calc doesn't give exact ans???

and question8d, i don't understand why they have used 2i+j+3k as the point a i thought A in the vector equation of a line is a point on the line, but they have used the direction vector of it???

Reply 590

Ilovemaths96

13

Original post by mmms95

you're talking about june 2014 r right? the markscheme is not using arc length, look at the presence of 2pi

sorry got my formulas mixed up. thanks

Reply 591

math42

20

Original post by Ilovemaths96

method for fining equation of line of intersecion of 2 planes?

Find the cross product of their normals as this is in the direction of both planes
This is your direction vector (well you can often cancel scalar common factors to get the lowest form direction vector)
Then to find a point of intersection you can generally just set x, y or z = 0 and solve the resulting simultaneous equations (the cartesian equation of each plane)

Reply 592

Ilovemaths96

13

Original post by 1 8 13 20 42

Find the cross product of their normals as this is in the direction of both planes
This is your direction vector (well you can often cancel scalar common factors to get the lowest form direction vector)
Then to find a point of intersection you can generally just set x, y or z = 0 and solve the resulting simultaneous equations (the cartesian equation of each plane)

Thanks

Reply 593

username1162972

18

Original post by Gome44

I am fairly certain you mean FLHR given your explaination :tongue:

.

This is the grip rule:

Na grip rule.

Reply 594

chughes17

2

Original post by 1 8 13 20 42

Find the cross product of their normals as this is in the direction of both planes
This is your direction vector (well you can often cancel scalar common factors to get the lowest form direction vector)
Then to find a point of intersection you can generally just set x, y or z = 0 and solve the resulting simultaneous equations (the cartesian equation of each plane)

Sorry how can we just set x y or z to 0? How do we know we can do this, and also set it to 0 in what? Both planes' equations?

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Reply 595

math42

20

Original post by chughes17

Sorry how can we just set x y or z to 0? How do we know we can do this, and also set it to 0 in what? Both planes' equations?

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Yes to both planes' equations. I am not quite sure; I have some ideas but on a practical level it is an ends justifies the means thing. If you set x = 0, for instance, and this generates y and z values that satisfy both plane equations, then it is clear that setting x = 0 was valid.

It is quite simple to see that setting x = 0 in one plane (unless the equation of the plane is x = c for some constant that does not equal 0) will generate valid values so long as there are variable y and z terms. As for intersecting planes, assuming that x, y, or z = 0 (unless one is a constant as said before) will not do any harm usually. I believe it is possible that this could be invalid, but if it is, this invalidity will be presented to you by your calculations not working out and you will need to try a different avenue. I've tried looking at the general case algebraically and I think there are possible problems depending on the relationships between the coefficients of each term, but typically if setting one value equal to zero doesn't work you can probably try the others and it will.

I don't think the zero approach has ever not worked in an edexcel question; I imagine if it didn't there would be some other more obvious quick way to find an intersection point.