• Best of luck to the class of 2024 for their HSC exams. You got this!
    Let us know your thoughts on the HSC exams here
  • YOU can help the next generation of students in the community!
    Share your trial papers and notes on our Notes & Resources page
MedVision ad

Prelim 2016 Maths Help Thread (3 Viewers)

Status
Not open for further replies.

Trebla

Administrator
Administrator
Joined
Feb 16, 2005
Messages
8,375
Gender
Male
HSC
2006
Oh shit my condition

y=squareroot of (x) +2, y<_2
wait wtf...
When you took the square root, why did you choose the positive and not the negative one? Think about which one makes sense given the condition imposed.
 

eyeseeyou

Well-Known Member
Joined
Nov 20, 2015
Messages
4,125
Location
Space
Gender
Undisclosed
HSC
N/A
When you took the square root, why did you choose the positive and not the negative one? Think about which one makes sense given the condition imposed.
idk this is pissing me off

Show me your working out Trebla

BTW you should be a tutor Trebla
 

leehuan

Well-Known Member
Joined
May 31, 2014
Messages
5,805
Gender
Male
HSC
2015
idk this is pissing me off

Show me your working out Trebla

BTW you should be a tutor Trebla
Read what he said again. He clearly said think about which one makes sense given the condition imposed

To spell it out for you: That means, look at your condition, and figure out why it has to be the negative

This is what I mean by doing things that are beyond your level. If you don't know how the basics work that backbone it, don't bother trying by yourself or just the people on here.
 

Trebla

Administrator
Administrator
Joined
Feb 16, 2005
Messages
8,375
Gender
Male
HSC
2006
idk this is pissing me off

Show me your working out Trebla

BTW you should be a tutor Trebla
You won't learn if I just spoonfeed you the answer.

I'll try it here

y=(x-2)^2, x <_ 2
Switch x and y around
x=(y-2)^2, y <_ 2
Squareroot of x=y-2, x <_2
squareroot of x+2=y
y=squareroot of (x) +2
Given our condition is x <_2 we can only have one case

Okay wtf am I doing wrong

Get carrotsticks to help us out
In the bolded part, why did you pick only the positive square root? Why did you ignore/reject the negative square root?
 

eyeseeyou

Well-Known Member
Joined
Nov 20, 2015
Messages
4,125
Location
Space
Gender
Undisclosed
HSC
N/A
You won't learn if I just spoonfeed you the answer.


In the bolded part, why did you pick only the positive square root? Why did you ignore/reject the negative square root?
The condition is wrong, it's y<_2

Also it's not really spoonfeeding me if I do the question and get it wrong and someone shows me how to do it correctly
 

Trebla

Administrator
Administrator
Joined
Feb 16, 2005
Messages
8,375
Gender
Male
HSC
2006
The condition is wrong, it's y<_2

Also it's not really spoonfeeding me if I do the question and get it wrong and someone shows me how to do it correctly
Your working is fine except that one part. If you actually tried to answer my question you will be able to understand why.
 

eyeseeyou

Well-Known Member
Joined
Nov 20, 2015
Messages
4,125
Location
Space
Gender
Undisclosed
HSC
N/A
Where are the following formulas derived from:

1. sin(a+b)=sinacosb+sinbcosa
2. sin(a-b)=sinacosb-sinbosa
3. cos(a+b)=cosacosb-sinasinb
4.cos(a-b)=cosacosb+sinasinb
5. tan(a+b)=(tana+tanb)/(1-tanatanb)
6. tan(a-b)=(tana-tanb/1+tanatanb)
 

InteGrand

Well-Known Member
Joined
Dec 11, 2014
Messages
6,109
Gender
Male
HSC
N/A
Where are the following formulas derived from:

1. sin(a+b)=sinacosb+sinbcosa
2. sin(a-b)=sinacosb-sinbosa
3. cos(a+b)=cosacosb-sinasinb
4.cos(a-b)=cosacosb+sinasinb
5. tan(a+b)=(tana+tanb)/(1-tanatanb)
6. tan(a-b)=(tana-tanb/1+tanatanb)
A derivation based on the unit circle may be found in the Year 11 3U Pender (Cambridge) textbook.

(Also you should be able to see that some of them follow immediately from the others once you've derived those, using properties of the trig. functions.)
 

Paradoxica

-insert title here-
Joined
Jun 19, 2014
Messages
2,556
Location
Outside reality
Gender
Male
HSC
2016
Where are the following formulas derived from:

1. sin(a+b)=sinacosb+sinbcosa
2. sin(a-b)=sinacosb-sinbosa
3. cos(a+b)=cosacosb-sinasinb
4.cos(a-b)=cosacosb+sinasinb
5. tan(a+b)=(tana+tanb)/(1-tanatanb)
6. tan(a-b)=(tana-tanb/1+tanatanb)
Why don't you prove them yourself.
 

eyeseeyou

Well-Known Member
Joined
Nov 20, 2015
Messages
4,125
Location
Space
Gender
Undisclosed
HSC
N/A
What about the double angle formula for Tan:

tan2(theta)=2tan(theta)/1-tan^2(theta)
 

InteGrand

Well-Known Member
Joined
Dec 11, 2014
Messages
6,109
Gender
Male
HSC
N/A
What about the double angle formula for Tan:

tan2(theta)=2tan(theta)/1-tan^2(theta)
The double angle formulas follow by letting a = b in each of the trig. expansion identities for f(a+b).
 

eyeseeyou

Well-Known Member
Joined
Nov 20, 2015
Messages
4,125
Location
Space
Gender
Undisclosed
HSC
N/A
What about product to sum

2sinAcosB=sin(A+B)+sin(A-B)

Do you just expand this out?
 

Trebla

Administrator
Administrator
Joined
Feb 16, 2005
Messages
8,375
Gender
Male
HSC
2006
Where are the following formulas derived from:

1. sin(a+b)=sinacosb+sinbcosa
2. sin(a-b)=sinacosb-sinbosa
3. cos(a+b)=cosacosb-sinasinb
4.cos(a-b)=cosacosb+sinasinb
5. tan(a+b)=(tana+tanb)/(1-tanatanb)
6. tan(a-b)=(tana-tanb/1+tanatanb)
See the 2U/3U syllabus or a textbook for the derivation
 
Status
Not open for further replies.

Users Who Are Viewing This Thread (Users: 0, Guests: 3)

Top