kingjewel1

sorry i don't follow if i'm using tan^2x+1=sec^2x why wouldn't it be 2(sec^2x)=2(tan^2x+1)?

how would i show that the values of x at which sinxe^(-sinx) has stationary points form an arithmetic sequence. I've so far worked out dy/dx=cosxe^-sinx(1-sinx)=0 so cosx.e^-sinx= and sinx=0 arcsin0=pi,2pi,3pi,4pi,etc so cospi.e^-sinpi=0 cos2pi.e^-sin2pi=1 cos3pi.e^-sin3pi=0 cos4pi.e^-sin4pi=1 therefore it is a repeating sequence and common difference 1,-1 but i don't think this is correct as again (im not sure how to solve (cosxe^-sinx(1-sinx)=0)) any ideas? thanks for any help

cheers for the help! so secx(2sec^2-1)=-1 => 2sec^2-1 =-cosx 'using tan^2x+1=sec^2 2(1+tan^2x)-1=-cosx 2+2sin^2x/cos^2x=-cosx 'using tan^2x=sin^2x/cos^2x 2(cos^2x+sin^2x)=-cos^2x ' using c^2+s^2=1 -2=cos^3x that seems to be it. but i don't see how it could be that. if between -pi and pi, then there would be toooo many solutions! hundreds even! no?

thanks guys!!! I only just realised that i had to treat the two parts cosx=o and ln(x+1) as separate functions. Sorry i'm new to this type of stuff. I find problems with solving a function that is not equal to 0 ie. secx(2secx^2-1)=-1 what do i do with this beauty to find its solutions? is it secx=-1 and secx=sqrt-2 ,which is impossible?

Hi there If i had a function in the format cos(ln(x+1)) =0 how would i go about trying to solve for the solutions (roots) I can see there are three roots but i'm not sure how to solve it. ps. how do you solve secx(2sec^2x-1)=0 as ih happens i know it has no solutions, but how would i go about showing this. where can i look this stuff up thanks guys!

does anyone have a list of ligands from strongest to weakest or know where to get one¿

If i remember rightly sodium tetrahydridoborate is a selective reducer. The conditions aren't anything special for it so i don't see why you need the methanol. Unless it is that, to do with the reaction yield.

mercaptobutanone and dimethyl sulphide among others. not easy to make those two

pH is calculated at ALL concentrations: that is why we have a scale from 10^1 to 10^14 in log base ten. Use pH of a strong acid (HCl or H2SO4) = -lg[H+] in words: minus log base ten of hydrogen ion concentration. Weak acids : pH =-lg sqrt([acid].Ka) for weak acids all you need to know is their Ka value (their acid dissociation Konstant) and their concentration.

Do you mean: something that will still give a positive test in high temperatures? Magnesium at those temperatures will react with steam and produce magnesium hydroxide. This is pretty insoluble (not sure how insoluble). If you tested for its pH with universal indicator it would be purple. Hope that helps

The hydrates of Cu compounds are due to water ligands. The water molecule makes a dative bond in the Cu's d orbital. Six of these H20 molecules can comfortably attack the Cu. As mentioned above, H2O is the not the only ligand, EDTA being one of the strongest. Things like NH3- and CN- also are ligands.

thanks guy very much! Yeah it seems quite logical that with just 1 mole of zinc it would have to have an oxidation state of +4 and that is rediculous. Apparently it is THERMODYNAMICALLY unstable but KINETICALLY stable. I've never really understood the difference between the two, but i would have thought it was kinetically unstable due to such a high activation energy. :S

Interesting. I think though, the question is looking for a reason on the microscopic level if you know what i mean...

How do you mean?

Showing that both iron (III) and iron (II) ions in solution should react with zinc to give iron metal. Zn=>Zn2+ e Fe3+ +e=>Fe2+ + 2e=>Fe Instead only iron (II) irons are produced. 2Fe3+ +Zn==>Fe2+ + Zn2+ Apparently iron metal it is not made but why not? only 1 point question, has me stumpped. Help me with the half equations for the iron above please. thanks guys

well they do exist: solar batteries are recharged on the move. Then again! You may like to transport some uranium around with you...

Mobile phone operator zim" in my country is saying it has more than four million clients. If a phone number is 9 digits long and always starts with a 6... How is this possible?

you can use the generic fomula for natural logarithm integration LN(a•x)^p dx ⇒ x•LN(a•x)^1/2 - p• int LN(a•x)^-1/2 dx that is the standard answer but as dave said it won't give you a definite answer.

In this case, i think it would be a matter of perception rather than science. The wife would think that it is hot as you tell her the reason you hadn't added the milk was so as not to let her coffee get cold. Physically there is only the difference in time. Let it cool now, or let it cool later. Thermodynamically speaking it is exactly the same. The milk warms so gains energy from the ambient. The coffee cools and so loses energy to its surroundings. Doesn't matter which way you do it. it's the same as the enthalpies are equal regardless of the route. OneStone

Great stuff! I'll keep it in mind.

aww Cheers! I've been trying to figure out a generic formula for the integration of that type! Yeh, you know; i was just about to fall asleep and then suddenly the meaning of pi popped into my head. I'd previously thought it was easy to approximate by areas of polygons but it just occured to me how i could do it this way. I see you're in london "The Rebel". I'm doing my alevels and was offered a place at UCL to do maths. I'm seriously contemplating taking them up. What do you think? would you recommend it?

y=(-x^2+1)^1/2 How do i integrate this guy from 0 to 1? since the x^2 has a negative constant, would you need to integrate i? like this [ix^3/3+x] OneStone

A true figure is very difficult to come by; especially from china and USSR. The death toll counts primarily only men in the armies and not the civilians that perished in the defense of eg stalingrad. I'd put 25 to 40 percent ontop of any of their figures.

It's important to realise that in nature that badly deformed infants are ostracised by the pack and left defenseless to die. It is also relevant to this topic that had the mother of mozart decided to have an abortion because he was terminally ill... one of the greatest musically talented minds in the world would never have come to fruition. Where would you stop? This is similar to predicting the future. Leave it up to God all mighty to decide when to take his children. As you say, in centuries gone by there were no means to artificially keep a baby alive, it simply died. Now we are landed with the choice... One way or the other it is wrong. Wrong to let it live, but wrong to let die. Political policy will eventually rule in favour of some cases. It comes in the end.

Aw cheers! Thanks a lot!