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/sci/ - Science & Math

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2829396 No.2829396 [Reply] [Original]

The line L1 is given by (3i+5k)+t(-2i+j-5k)

The point P has position vector (-i+2j-5k) and the point Q has position vector (-3i+8j-k).

Find the equation of the line L2 joining the points P and Q. Hence find the acute angle between lines L1 and L2.

Halp /sci/

inb4 homework, it's revision for exam

>> No.2829399

>>2829396

I took vector algebra. Understood none of it. Realized it wasn't relevant to anything other than itself. Managed a "B" Then forgot it all.

MOST. USELESS. CLASS. EVER>

>> No.2829401
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2829401

y u revise for c4 so early

>> No.2829408

L2 is going to be Q-P

so now u have L1 and L2. then use L1.L2 = |L1| |L2| cos x

>> No.2829417

>>2829401
Because C4 is so fun!

Not as good as Stats 1 mind you.

>> No.2829420

>>2829417

haha stats is fun but it could fuck you up in the ass anytime it wants, if you know what i mean.

anyway doing some vectors in c4 right now as well.

>> No.2829421

>>2829420
Haha, true. But still.

And what board are you on? (MEI here).

>> No.2829422

>>2829421

Edexcel. its not too bad. where do you live

>> No.2829423

once you find the equation of the line you can use the dot product to find the angle

u1v1+u2v2+u3v3 = ||u|| * ||v|| * cos(theta)

where the double line thing indicates magnitude

god help you if you don't know what magnitude is or how you calculate it

>> No.2829428

>>2829399
Vector algebra is one of the most practical, applicable and important classes there is, in terms of usefulness for subjects beyond math.

>> No.2829429

I detect USYD linear algebra fag

>> No.2829430
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2829430

>>2829422
Here, there and everywhere.

>> No.2829434

Doing MEI too and from nottingham. FP2 can lick my balls...

>> No.2829441

>>2829423

I do, but putting a few values into an equation seems a bit straightforward for 8 marks (11% of paper)

>> No.2829453

>>2829441

well you cant just go hurr durr i put this number in this formula and i get da marks. you have to understand what going on between the 2 lines and work out the method and maybe even visualize it. if you can do that then yes you deserve the 8 marks.
also most of the paper is vectors and integration anyway

>> No.2829504

http://www.mei.org.uk/index.php?section=papers&page=alevelpapers

every single past paper to pretty much every MEI spec module for anyone who is on MEI who didnt know about this.