Products as sums or differences (2 Viewers)

Carrotsticks · Jan 16, 2012

812 said:
Can you still recall the download link for it?

http://www.dessci.com/en/products/mathtype/?utm_nooverride=1&gclid=CL2B9szH060CFY-FpAodBH_Ong

812 · Jan 16, 2012

Sigh. I downloaded it but when I ran the exe, it said it couldn't find the path.

Stupid government school laptop.....

Carrotsticks · Jan 16, 2012

812 said:
Sigh. I downloaded it but when I ran the exe, it said it couldn't find the path.

Stupid government school laptop.....

What was the error message exactly?

812 · Jan 16, 2012

I can run the exe, but after I click agree with terms and conditions and "next"

"The system cannot find the path specified." pops up
when I click "OK",
"Error Executing the Specified Program "setup.exe"" pops up
when I click "OK" again,
"Unable to execute the specified command line!" pops up
when I click "OK", the application closes by itself.

Carrotsticks · Jan 16, 2012

812 said:
I can run the exe, but after I click agree with terms and conditions and "next"

"The system cannot find the path specified." pops up
when I click "OK",
"Error Executing the Specified Program "setup.exe"" pops up
when I click "OK" again,
"Unable to execute the specified command line!" pops up
when I click "OK", the application closes by itself.

Perhaps once school resumes, you can take it to the IT Crowd at school to see if they can fix it.

PS: I love that show.

812 · Jan 16, 2012

I made a windows bat file that'll let a specific folder run exe, but I don't have full admin privileges...

So I don't think I can install. But if I installed it on a full admin computer and then copied the whole folder across, then it should work.

812 · Jan 16, 2012

I've fully hacked my laptop before because I knew the BIOS password so I could change pretty much any settings using a usb boot disk. Then DET took our laptops in to re-image it and they changed the BIOS password in the process...

Can't get full admin now.

Carrotsticks · Jan 16, 2012

Here is my MathType folder. It may/may not work for you.

http://www.mediafire.com/?7s5lm1as1qum3rx

kingkong123 · Jan 16, 2012

SpiralFlex said:
Here's a trick to remember them.

First of all I will list the formulae out.

$\sin A+\sin B=2\sin\frac{A+B}{2}\cos\frac{A-B}{2}$

$\sin A- \sin B = 2\cos\frac{A+B}{2}\sin\frac{A-B}{2}$

$\cos A+ \cos B = 2\cos\frac{A+B}{2}\cos\frac{A-B}{2}$

$\cos A- \cos B = -2\sin\frac{A+B}{2}\sin\frac{A-B}{2}$

Now let's inspect these formulae.

We know we have a combination of messy expansions. But what can we see that is similar? Looking closely I can see that the terms on the RHS will always be first [The average of the sums of A and B] then [The average of the differences of A and B]

Now all we need to do is to memorise the trigonometric identity.

In short,

[S+S]=2[SC]
[S-S]=2[CS]

[C+C]=2[CC]
[C-C]=-2[SS]

Note: The cosines are the ones with the same identities together. In other words you can think of "same sex marriage".

Now, let us go backwards!

$2\sin A \cos B=\sin(A+B)+\sin (A-B)$

$2\cos A \sin B=\sin (A+B)-\sin (A-B)$

$2\cos A\cos B =\cos (A+B)+\cos (A-B)$

$-2\sin A \sin B=\cos (A+B)-\cos(A-B)$

On first examination,

We see on RHS again! We have the same terms. You have your trigonometric function then, A+B and A-B.

So they stay the same.

Now,

2[SC]=[S+S]

2[CS]=[S-S]

2[CC]=[C+C]

-2[SS]=[C-C]

Now there is a pattern with going back and forth, but I will let you figure that out for yourself. Connect the dots.

this man is a genius

Drongoski · Jan 16, 2012

Carrots

Thanks for the info on MathType. Appreciate it.

Your dad didn't appear as much in yesterday's episode of "Once upon a Time ...".

Carrotsticks · Jan 16, 2012

Drongoski said:
Carrots

Thanks for the info on MathType. Appreciate it.

Your dad didn't appear as much in yesterday's episode of "Once upon a Time ...".

You're welcome. It's very useful for writing exam papers. Much superior to Microsoft Word's Equation Editor.

Yeah I saw. But I guess the focus was the story of the parents and the drug dealers.

I think he will appear more in the Episode 3.

812 · Jan 16, 2012

Carrotsticks said:
Here is my MathType folder. It may/may not work for you.

http://www.mediafire.com/?7s5lm1as1qum3rx

Doesn't work

When I click the exe, nothing happens.

Thank you for uploading that though

Drongoski · Jan 17, 2012

Carrotsticks said:
You're welcome. It's very useful for writing exam papers. Much superior to Microsoft Word's Equation Editor.

Yeah I saw. But I guess the focus was the story of the parents and the drug dealers.

I think he will appear more in the Episode 3.

If your dad is not careful, he may end up a movie star.

It would be nice if they have another series on the boatpeople who made good. That would provide a feel-good chronicle for a change.

I personally know of a Vietnamese (ethnic Chinese) who were at Pulau Bidong off east coast of Malaysia before being accepted into Australia. All his children are graduates: 2 doctors, 1 architect, 1 engineer, 1 in IT and I don't know what happened to the youngest one. For a few years he had the Best & Less Chinese Restaurant at Earlwood but has sold the business. I'm sure there are many others who have gone on to make good.

Carrotsticks · Jan 17, 2012

Drongoski said:
If your dad is not careful, they may talent scout him for a movie role.

It would be nice if they have another series on the boatpeople who made good. That would provide a feel-good chronicle for a change.

I personally know of a Vietnamese (ethnic Chinese) who were at Pulau Bidong off east coast of Malaysia before being accepted into Australia. All his children are graduates: 2 doctors, 1 architect, 1 engineer, 1 in IT and I don't know what happened to the youngest one. For a few years he had the Best & Less Chinese Restaurant at Earlwood but has sold the business. I'm sure there are many others who have gone on to make good.

Haha, I'm quite sure he won't appear in any movies

My dad was also a boat person and was put into Pulau Bidong (he too escaped Vietnam after doing his service in the War).

It's amazing seeing people who started with nothing... slowly working their way up to become very well off. A documentary showing such stories would inspire many.

Drongoski · Jan 17, 2012

You yourself are an example of the many (on the way to) making good, and unlike Hoang and the other one(whose dad broke down & wept), have not caused your parents grief. In Confucian society, that's what a filial son should be like. Take a bow.

Carrotsticks · Jan 17, 2012

Drongoski said:
You yourself are an example of the many (on the way to) making good.

Haha, thank you for that.

Webbmiester · Jan 18, 2012

i dont get how -(1+cosx) becomes 2cos^2(x/2)

SpiralFlex · Jan 18, 2012

You mean why

$-(1+\cos x)=-2\cos^2 \frac{x}{2}$

Using the double angle identity,

$\cos x = \cos^2 \frac{x}{2}-\sin^2 \frac{x}{2}$

$\cos x = \cos^2 \frac{x}{2} - (1-\cos^2 \frac{x}{2})$

$\therefore \cos x=2\cos^2 \frac{x}{2}-1$

$\therefore \cos x+1=2\cos^2 \frac{x}{2}$

It then follows,

$-(\cos x+1)=-2\cos^2 \frac{x}{2}$

osak23 · Jan 18, 2012

had the same problem
oooooo
a lot clearer now
thanks!!!!!!

cutemouse · Jan 18, 2012

Carrotsticks said:
You're welcome. It's very useful for writing exam papers. Much superior to Microsoft Word's Equation Editor.

I think proper latex is better

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