Discussion about math, puzzles, games and fun. Useful symbols: ÷ × ½ √ ∞ ≠ ≤ ≥ ≈ ⇒ ± ∈ Δ θ ∴ ∑ ∫ π -¹ ² ³ °

You are not logged in.

- Topics: Active | Unanswered

**Amrita****Member**- From: Westing's House
- Registered: 2014-04-30
- Posts: 814

prove it.

**In mathematics the art of proposing a question must be held of higher value than solving it. - Georg Cantor (1845-1918)**

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

hi Amrita,

Do you know the formulas for sinX + sinY and sinX - sinY ?

Use difference of two squares and these two formulas.

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**Amrita****Member**- From: Westing's House
- Registered: 2014-04-30
- Posts: 814

can u plz tell me the formulae?

**In mathematics the art of proposing a question must be held of higher value than solving it. - Georg Cantor (1845-1918)**

Offline

**Amrita****Member**- From: Westing's House
- Registered: 2014-04-30
- Posts: 814

hello bobym,how r u?talking 2 u after a long time.

**In mathematics the art of proposing a question must be held of higher value than solving it. - Georg Cantor (1845-1918)**

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 88,882

Hi;

Have not seen you in a few days.

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**Amrita****Member**- From: Westing's House
- Registered: 2014-04-30
- Posts: 814

actually my 1 GB net in dongle was finished.can u plz tell me the formula bob bundy was talking about?

- Georg Cantor (1845-1918)

Offline

**bobbym****Administrator**- From: Bumpkinland
- Registered: 2009-04-12
- Posts: 88,882

The only one I know offhand is:

**In mathematics, you don't understand things. You just get used to them.**

**I agree with you regarding the satisfaction and importance of actually computing some numbers. I can't tell you how often I see time and money wasted because someone didn't bother to run the numbers.**

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

That looks like the ones.

Do you want me to show where they come from? Starting with the compound angle formulas ....

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**Amrita****Member**- From: Westing's House
- Registered: 2014-04-30
- Posts: 814

thnx. can u plz help with this sum? if x+a is the hcf of x^2 + px +q and x^2 + lx + m,find the value of a.

- Georg Cantor (1845-1918)

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

I've done this recently for someone else, maybe Agnishom??

Just looking it up.................

Bob

You cannot teach a man anything; you can only help him find it within himself..........Galileo Galilei

Offline

**Amrita****Member**- From: Westing's House
- Registered: 2014-04-30
- Posts: 814

yes bob,u can show them.i would like 2 know it.

- Georg Cantor (1845-1918)

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

Offline

bob bundy wrote:

I've done this recently for someone else, maybe Agnishom??

Just looking it up.................

Bob

Yes, you have. Because my Watari gave me this sum and I gave Amrita this sum

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

Offline

Please help me with proving this:

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

hi Agnishom,

I haven't tried this yet (sound familiar ?) but this should work.

Start with (sin^2(x) + cos^2(x)) ^6 to get an expression for sin^6 + cos^6.

Use this to remove those terms from the expression.

Now do the same again with (sin^2(x) + cos^2(x)) ^4 to remove the fourth powers.

What's left will only have sin^2 and cos^2 terms so you should be able to twist it into the required result.

Hope I'm right. :fingers crossed smiley

Bob

I'm hoping the odd powers cancel out.

Offline

Start with (sin^2(x) + cos^2(x)) ^6 to get an expression for sin^6 + cos^6.

That is tedious.

What is the fingers crossed smiley?

'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,606

Agnishom wrote:

bob bundy wrote:I've done this recently for someone else, maybe Agnishom??

Just looking it up.................

Bob

Yes, you have. Because my Watari gave me this sum and I gave Amrita this sum

Watari? Like from Death Note.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**ShivamS****Member**- Registered: 2011-02-07
- Posts: 3,610

Agnishom wrote:

What is the fingers crossed smiley?

It is someone crossing their fingers.

Offline

anonimnystefy wrote:

Agnishom wrote:bob bundy wrote:I've done this recently for someone else, maybe Agnishom??

Just looking it up.................

Bob

Yes, you have. Because my Watari gave me this sum and I gave Amrita this sum

Watari? Like from Death Note.

Yes, I call her Watari because I call myself L

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,606

Really? That's cool. I'm not sure which character I have the most in common with.

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

Agnishom wrote:

That is tedious.

Yes, but then again, you should have said "Have you got your glasses on Bob? I think you meant:

and

Then start with the LHS of the required identity, multiply out the brackets, cancel some bits, factorise and use s^2 + c^2 = 1 lots of times and you'll get to

3 + 6 + 4 = 13 QED.

So get on with it!

Bob

Offline

I did it! Thank You!

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

Offline

**bob bundy****Moderator**- Registered: 2010-06-20
- Posts: 6,469

Excellent!

Bob

Offline

Please help me with proving

'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'

'You have made another human being happy. There is no greater accomplishment.' -bobbym

Offline

**anonimnystefy****Real Member**- From: The Foundation
- Registered: 2011-05-23
- Posts: 15,606

Hi Agnishom

Here lies the reader who will never open this book. He is forever dead.

Taking a new step, uttering a new word, is what people fear most. ― Fyodor Dostoyevsky, Crime and Punishment

Offline