Melody

Inverse cos is the same as arc cos.

Press 2nd acos number

Or

Just type     acos (number)=

Thank you Max,

It looks like it might be useful but I will have to take a better look before I really know :)

Hi, thanks for repsonding to my answer, we always like askers to respond because then we are certain we know I answers have been read, considered and hopefully tearned from. :))

I do not think I talked about "a system of negative numbers"  There is no such thing......

I think that you cannot quite see the relevance of everything I have said, and that is fine, I see the relevance but you do not really need to. :)

YES you do need to understand how numbers work and why different calculators give different answers.  It is always up to the user to get the best out of his machines :)

As far as the authors statement goes, I will repeat:

"He means it is easy to see because i^2=-1 but he is wrong because he has not used brackets properly.

By not using brackets properly he has not followed proper convention.

He has overlooked this because, in the context of what he was talking, his meaning was clear, he thought so anyway :)"

Hi Majid,

I am not going to attempt your calculus but it is great to finally see you posting on the forum  :D

I always like looking at these answers too if anyone want to have a go. :)

When will 3.00+.25x and 4.50+.10x cast the same amount of money

Well they have to be equal don't they:)

\(3.00+.25x = 4.50+.10x\)

 subtract 0.10x from BOTH sides

\(3.00+0.15x = 4.50\)

NOW subtract 3.00 from both sides and then think about how to finish it :)

Hi guest,

Could you (or someone else) please elaborate on the first step.  Thanks :)

Hi Helpls, welcome to our web2 forum :)

what is the derivative of 1+0.00003t+0.0000004t^2? with steps please

The derivative of 1 is 0

The derivative of  0.00003t

\(\frac{d}{dx}\;0.00003t^1\\ =1*0.00003t^{1-1}\\ =0.00003t^{0}\\ =0.00003*1\\ =0.00003\\\)

and

The derivative of  0.0000004t^2 is  

\(=2* 0.0000004t^{2-1}  \\ = 0.0000008t  \\\)

So

\(\frac{d}{dx}\;[1+0.00003t+0.0000004t^2] =0.00003+0.0000008t\\\)

Thanks very much Max.

It is really great to know about all these wonderful internet tools.

I did not know about either of these sites before :)

THANKS EP !!!

The integral calculator that EP found works and absolute treat!

Check it out !!!

Oh I just reread EP's suggestion.

Maybe they do it much better there.

I must check it out - thanks EP