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Edexcel FP3 - 27th June, 2016

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Original post by Hineshtailor
do i consider the directrix which is closest to each foci or do i do it to only one directrix?


Well for b), they want you to consider one general point, so you'd use the directrix closest to one focus, then the other directrix.

If that's what you mean
Original post by Geraer100
The perpendicular distance between a point and a plane is the same as the shortest distance between a point and a plane?


Yah
Original post by Armpits
Yah


thanks alot, you got any questions that are kinda tricky/ interesting from past papers?
Original post by Hineshtailor
thanks alot, you got any questions that are kinda tricky/ interesting from past papers?


https://mathsmartinthomas.files.wordpress.com/2014/12/extra_fp3_papers.pdf

Q.73 p.34

7.c)

Pretty interesting.
Original post by Armpits
Yah

Okay, does it apply also to distance between planes, lines? I mean perpendicular d=shortest d?
June 2013, q8 first part the first method used in the mark scheme is really confusing, if someone can explain that, I will be really grateful!


u got the solution for them also for 7c would you use the direction vector of QR and then add the position vector P? seeing as QR seems to be parallel to PS.


and damn how come i never knew all these papers were still around yet i haven't done them :s-smilie:
Original post by Geraer100
The perpendicular distance between a point and a plane is the same as the shortest distance between a point and a plane?


Yes, remember the formula's in the booklet.
Original post by somevirtualguy
Yes, remember the formula's in the booklet.

Thanks
Oh I see, but does this apply for the distance between line and plane or two planes or two lines? Because in the book, they used different methods to find the shortest distance and perpendicular distance between two parallel lines?


nice, interesting question (had to take a peak at the MS and saw they equated the planes lol) but for the last part theyre saying the area of a pyramid is 1/3 (a.bxc)?
Original post by Geraer100
Thanks
Oh I see, but does this apply for the distance between line and plane or two planes or two lines? Because in the book, they used different methods to find the shortest distance and perpendicular distance between two parallel lines?


The formula is specifically for the distance between a line and a plane.

The distance between two lines is a C4 method.

The distance between two parallel lines is very similar, if not the same now I think about it. Use a specific point on one line, find the general point on the other line, find the vector from the specific point to the general point, then dot product equals 0 for the specific to general and the direction of the lines. Then you should be able to find the distance.

The distance between two planes, well once you've thought about it unless they're perfectly parallel all planes eventually intersect......

And then of course there's that nasty formula you need to remember for the distance between two skew lines :smile:
can someone help me with june 2012 question 6d) pls
i know that min and max values for costheta is 1 and -1 but i dont understand the inequalities
(edited 7 years ago)
Original post by Hineshtailor
nice, interesting question (had to take a peak at the MS and saw they equated the planes lol) but for the last part theyre saying the area of a pyramid is 1/3 (a.bxc)?


where did you find the mark scheme?
Maan I've ****ed myself for this, expecting a low A
Original post by somevirtualguy
The formula is specifically for the distance between a line and a plane.

The distance between two lines is a C4 method.

The distance between two parallel lines is very similar, if not the same now I think about it. Use a specific point on one line, find the general point on the other line, find the vector from the specific point to the general point, then dot product equals 0 for the specific to general and the direction of the lines. Then you should be able to find the distance.

The distance between two planes, well once you've thought about it unless they're perfectly parallel all planes eventually intersect......

And then of course there's that nasty formula you need to remember for the distance between two skew lines :smile:


Really thanks for the detailed explanation!
and the dot product is equal to 0 because it's the perpendicular distance(which is the same as the shortest distance) no?

But one thing regarding to the shortest distance and the perpendicular distance, I am still a bit confused because, I know the shortest distance is the same as perpendicular distance when we are talking about the distance from a point to plane/line,
But what about when it's regarding to the distance between two planes or a line and a plane, are the perpendicular distances between them the same as the shortest distances between them?

Sorry if the question is silly
Original post by Geraer100
Really thanks for the detailed explanation!
and the dot product is equal to 0 because it's the perpendicular distance(which is the same as the shortest distance) no?

But one thing regarding to the shortest distance and the perpendicular distance, I am still a bit confused because, I know the shortest distance is the same as perpendicular distance when we are talking about the distance from a point to plane/line,
But what about when it's regarding to the distance between two planes or a line and a plane, are the perpendicular distances between them the same as the shortest distances between them?

Sorry if the question is silly


Honestly I don't have anything in my notes on finding the distance between two planes or a line and a plane. You only need to concern yourself with the distance between a point and a plane/line.

Regarding the distances between two lines, you'll either be asked to find the distance between two parallel lines or two skew ones.

And yes the dot product must equal 0 because cos(90) is 0.

Try visualising a line and the origin, no matter how you draw it, the shortest distance between the line and the origin will always be perpendicular to the line.

Hope this has helped


just wondering. seeing as it says it must go through P and that the direction vector is the same as the other one QR seeing as they are parallel does this mean i could just say r= position vector of P plus the direction vector QR
Original post by Hineshtailor
nice, interesting question (had to take a peak at the MS and saw they equated the planes lol) but for the last part theyre saying the area of a pyramid is 1/3 (a.bxc)?


Yeah I thought it was pretty cool how they just worked out the line of intersection of both planes.

Area of pyramid = 1/3(area of base) * h
Original post by Major-fury
just wondering. seeing as it says it must go through P and that the direction vector is the same as the other one QR seeing as they are parallel does this mean i could just say r= position vector of P plus the direction vector QR


yeah you can lol but, you only find that out the question after, i also assumed that at first

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