fp1 - what am I doing wronng?

[silver wharf]

this was on my paper

[muted ore]

<@&791435371564892232>

[muted ore]

blud how old are you 💀

[oak matrix]

why u lying

ur paper was in 1956

[silver wharf]

my nan was born in 1956

[cloud cedar]

my nan was born in 1938 if that help!!

[oak matrix]

ok before i help

what did u learn in chapter 1

[silver wharf]

you learn more vectors

[silver wharf]

damn 1938

[oak matrix]

are you OKrackles25

[silver wharf]

no I'm pianotate

pronouns int/egral

[oak matrix]

💀

[white aurora]

why not do dot product to get the angle

here

i found 1331

in my calc

[oak matrix]

because theres a faster way of doing it

if u want

sure

[white aurora]

ok i guess im stupid gg

im slow

[oak matrix]

nah ur method is fine

[white aurora]

icl this question is basically AS maths

[oak matrix]

exactly

[white aurora]

like you can solve it just knowing cosine rule
although not optimal but still

[tropic heron]

I checked everything

your calculation for sinc is wrong

i got something like 0.604...., not 0.45...

which gives exact answer of 1331

this is so long to check ibr

the examiner would crash out lol

a much easier method is

calculate any of the two direction vectors, say pr and pq (make sure they start from same point, in this case both vectors start from p)

then do 0.5 x cross product (also known as vector product) of the two vectors

because area = 1/2 u x v

where u and v are two direction vectors

also make sure

to convert the 2d vectors you found into 3d by writing 0 as z coordinate

so (x,y) can be written as (x,y, 0)

otherwise cross product cant be done

@muted ore

[muted ore]

I don’t remember what chapter one means

[tropic heron]

yo boss did it help

[muted ore]

Yeah that would’ve been quicker

[tropic heron]

0.5 x cross product gives area in one go

oh wait

does AS have cross product

[muted ore]

So we get the same three vertices so I must’ve made a calculation error?

Unless there is a +- issue with sin and cos identity?

[tropic heron]

bro I just said

where you went wrong

in your calculation of sinc

[muted ore]

Thanks

[muted ore]

Ohh that’s smart

[muted ore]

Sorry I was scrolling from top to bottom and replying

[tropic heron]

or you can use this shoelace formula

just plug the coordinates

[muted ore]

So the theee methods in order of usefulness are

1. Cross
2. Dot
3. My atrocity with cosine rule
   Agree?

[tropic heron]

but i don't think its in the mark scheme

[tropic heron]

yeah

[tropic heron]

well proving dot product involves

cosine rule atrocity

[muted ore]

Thanks

[tropic heron]

nws

[muted ore]

Maybe lowkey I should use dot just because I doubt cross will be on msrkscheme

What do you think?

[tropic heron]

cross should be there

fp1

i would be very surprised if it isn't

[tropic heron]

also one thing

be consistent

like when you were calculating

magnitudes

you were not consistently doing (x2 - x1)^2 + (y2 - y1)^2

you were swapping the orders of differences of x and y

this makes checking difficult lol

[oak matrix]

Yeahgetout

[tropic heron]

wtf

its like calculating gradients

y2-y1/x2 - x1

just plug in coordinates

[muted ore]

oh that maskes sense thanks

i appreciate it