MedVision ad

HSC 2012 MX1 Marathon #2 (archive) (2 Viewers)

nightweaver066

Well-Known Member
Joined
Jul 7, 2010
Messages
1,585
Gender
Male
HSC
2012
Re: HSC 2012 Marathon :)

parabola

next question:
simplify :
sin(A+B)sin(A-B)+cos(A+B)cos(A-B)
cos(A + B - (A - B))

= cos(A + B - A + B)

= cos2B

@Carrot (your first post), i believe that's what happened to my thread lol.
 

deswa1

Well-Known Member
Joined
Jul 12, 2011
Messages
2,256
Gender
Male
HSC
2012
Re: HSC 2012 Marathon :)

Consider the straight line y=x. You can multiply the RHS by x/x without changing its value. Thus the straight line becomes y=x^2/x which suddenly can't have a value of 0, even though the line hasn't changed and its still defined at x=0
 

AAEldar

Premium Member
Joined
Apr 5, 2010
Messages
2,246
Gender
Male
HSC
2011
Re: HSC 2012 Marathon :)

Consider the straight line y=x. You can multiply the RHS by x/x without changing its value. Thus the straight line becomes y=x^2/x which suddenly can't have a value of 0, even though the line hasn't changed and its still defined at x=0
No no no. You cannot just divide by x and assume that it takes on all real values. As soon as you divide by x you're assuming that it can't equal zero.
 

mirakon

nigga
Joined
Sep 18, 2009
Messages
4,221
Gender
Male
HSC
2011
Re: HSC 2012 Marathon :)

No no no. You cannot just divide by x and assume that it takes on all real values. As soon as you divide by x you're assuming that it can't equal zero.
Yep because x can be any value including zero so multiplying by x/x is erroneous
 

deswa1

Well-Known Member
Joined
Jul 12, 2011
Messages
2,256
Gender
Male
HSC
2012
Re: HSC 2012 Marathon :)

Yep because x can be any value including zero so multiplying by x/x is erroneous
Yep, whoops didn't think of that. Why then does wolfram show the curve continuous at 0?
 

barbernator

Active Member
Joined
Sep 13, 2010
Messages
1,439
Gender
Male
HSC
2012
Re: HSC 2012 Marathon :)

sorry for turning this thread into a pedantic fest, next question!

solve for x.

e^(2x) - 7e^(x) + 9 > 0 (difficulty: moderately intriguing)

highlight below for the answer:

the answer is in your head
 
Last edited:

Timske

Sequential
Joined
Nov 23, 2011
Messages
794
Gender
Male
HSC
2012
Uni Grad
2016
Re: HSC 2012 Marathon :)

sorry for turning this thread into a pedantic fest, next question!

solve for x.

e^(2x) - 7e^(x) + 9 > 0 (difficulty: moderately intriguing)

highlight below for the answer:

the answer is in your head
Is it
x < Ln(3.5 - sqrt(13)/2) and x > Ln(3.5 + sqrt(13)/2)

lol
 

Timske

Sequential
Joined
Nov 23, 2011
Messages
794
Gender
Male
HSC
2012
Uni Grad
2016
Re: HSC 2012 Marathon :)

Given f(x) = arccos(1/x)

State it's domain
 

Timske

Sequential
Joined
Nov 23, 2011
Messages
794
Gender
Male
HSC
2012
Uni Grad
2016
Re: HSC 2012 Marathon :)

Medium
 

Users Who Are Viewing This Thread (Users: 0, Guests: 2)

Top