Current Year 13 thread Mark I (2014-2015)

Not completely sure either, but I think it will involve multiplying the area of the triangle by the distance between D to the plane? Area x Length so should give a volume

And area of triangle is absintheta? Or 1/2 absintheta

I really like planes and vectors though lol, like it's so abstract but at the same time not

Ok, forgot to tell you this but:



My method for the volume is correct but you need to multiply it by 1/3 as well, not sure where that comes from...

That vector product looks confusing

Because if you did triangle by distance you'd get triangular prism

Tetrahedron is a third of that

Heyheyheyhey

I'm gonna be honest, not exactly sure what a tetrahedron looks like like fudge

Just looked it up, makes a bit more sense now!

Vector product is, but there's a way of remembering it. You still need to look out for minus signs, so many **** ups happen there lol

The way to remember it:

Let's take the $v_2w_3$ term, to get it, write the v and w column vectors next to each other, and cover the first row of it $(v_1, v_2)$ with your finger. Then you make a diagonal 'cross' between v and w, from top left to bottom right. Repeat for the next term - but the order is important; $v_2w_3-v_3w_2$ is the x component (first row) of the cross product. Then for the y component (second row), you cover the second row of v and w and make the cross again, remember the order is important!

Don't you mean v1w1.

Sounds like matrices work, covering up with the minds eye

Long time no see.

(I don't think we've actually talked that much but I just remember the Peppa Pig avatar)

Yeah, spotted my mistake and already edited it to make the correction!

So many places to mess up when you're doing vectors/planes

I've been so busy with A2/UCAS

How have you been?

Yeah, I couldn't answer a 7 marker on my paper because I didn't know what it was asking

It was annoying because I found out after what they wanted and it was just so easy

One of the best mathematicians in the year, some Chinese guy, didn't get an A* in A2 Maths (we do A2 in one year if you're doing FM). He made mistakes like reading $f'(x)$ as derivative and not inverse function

That's what we do (although I did mine in Year 11, resat C3 in Year 12, and doing all of FM this year)

f'(x) is derivative though wut, how could it be inverse hmm

Isn't f'(x) used to denote inverse function sometimes...?

Isn't f'(x) used to denote inverse function sometimes...?

f^-1(x) would always be the inverse on an A-Level exam.

Didn't know that haha

Ok, forgot to tell you this but:



My method for the volume is correct but you need to multiply it by 1/3 as well, not sure where that comes from...

Duuuddee, I need help with proof by induction!

I understand the process of 1. Proving it for one case, 2. Making an assumption say: (n=k and 2k+1 = 2m) and using the induction step (k+1) but how do you PROVE it? Is it supposed to end up looking like the assumption?

Duuuddee, I need help with proof by induction!

I understand the process of 1. Proving it for one case, 2. Making an assumption say: (n=k and 2k+1 = 2m) and using the induction step (k+1) but how do you PROVE it? Is it supposed to end up looking like the assumption?