Prelim 2016 Maths Help Thread (5 Viewers)

[eyeseeyou]

You needed to take the negative square root, since y needed to be ≤ 2.

Oh shit my condition

y=squareroot of (x) +2, y<_2
wait wtf...

 

[Trebla]

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]

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]

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]

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]

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]

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]

Your working is fine except that one part. If you actually tried to answer my question you will be able to understand why.

First or second question in my quote?

 

[Trebla]

First or second question in my quote?

Both

 

[eyeseeyou]

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]

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]

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]

What about the double angle formula for Tan:

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

 

[Trebla]

In the bolded part, why did you pick only the positive square root? Why did you ignore/reject the negative square root?

Pls answer my question

 

[InteGrand]

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]

What about product to sum

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

Do you just expand this out?

 

[leehuan]

Pls answer my question

Bumping and liking this because you need to stop ignoring Trebla @ eyeseeyou.

 

[Trebla]

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

 

[leehuan]

What about product to sum

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

Do you just expand this out?

Well the answer to that question is yes, just expand out the RHS

 

[InteGrand]

What about product to sum

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

Do you just expand this out?

Yeah.