Preliminary mathematics marathon (1 Viewer)

[hscishard]

Haha yeah the minus, I was like how the fuck can they relate? And then I realised w was common.

Oh. That was one quick edit...

 

[AAEldar]

Yay! Solved it

That's intense -_-

 

[ohexploitable]

That's intense -_-

Not really, the hard part was interpreting the question, the rest is easy.

 

[Trebla]

Prove that

tan(60º - x)tan (60º + x) = tan 3x / tan x

 

[ohexploitable]

Prove that

tan(60º - x)tan (60º + x) = tan 3x / tan x

 

[hscishard]

That even legit?

 

[ohexploitable]

That even legit?

Legit?

 

[hscishard]

I don't think you can modify both sides in a prove question.

 

[ohexploitable]

I thought it was only you can't assume they're equal and cross multiply and shit.

 

[hscishard]

Yea you definitely can't do that.

My old teacher told me once you choose one side, you can't change the other.

 

[ohexploitable]

Well you could probably work backwards... but... mathematically it's still correct.

 

[t00l]

Well you could probably work backwards... but... mathematically it's still correct.

you must choose one side only and turn it into the other side. (hence the "prove that" part of a question)

 

[mirakon]

Or you could bring LHS to one value.

Then bring RHS to a value.

If said values are equal Therefore LHS=RHS

 

[super.muppy]

yea thats what you do in these types of questions. on working out paper u make em meet in the middle and on the test paper you play with one side to meet the other (i.e. working backwards from your working out)

 

[fullonoob]

for those who dont know how to get tan3x
exploitable's method is perfectly valid
from the end of LHS, times top bottom by tanx, probably he hasnt realised this
it is rare in 3u but common in 4u so dont panic

 

[hscishard]

Awsome. Proving equations just go easier.

^what do you mean don't panic. What if we want to do 4unit :S

 

[fullonoob]

just this : pray to ullah

 

[Official]

Or you could bring LHS to one value.

Then bring RHS to a value.

If said values are equal Therefore LHS=RHS

This.

 

[ohexploitable]

Why won't 2011ers play?

New Question:

A parabola has coordinates x = t and y = t². Points P and Q correspond to t = -1 and t = 2 respectively. The tangents at P and Q intersect at R(0.5, -2). T is a point on the parabola between P and Q such that the tangent at T bisects QR. Show that the tangent at T is parallel to PQ.

 

[hscishard]

Gradient of chord = 4-1/2--1 = 1

x=t y=t^2
y=x^2
y'=2x

When y'=1, x = 0.5
f(0.5)=0.25

Line of tangent t y= x-0.25
Midpoint of PQ = (2+0.5)/2 ,(4+-2)/2 = (1.25,1)

Sub Midpoint into tangent line, LHS=RHS
Therefore tangent T bisects PQ
Thats the shitness of show questions.
What's the other way?