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Primarygun

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Posts posted by Primarygun

  1. Thanks to DQW, my prove is completed :P.

    When we prove, we usually do from the backward first.

    With the given equation, try to split it into some triangles, some other laws.

    For example, if I splitted and found that I need to prove is XY^2+XZ^2=XY^2,

    then construct the responsible triangle and then prove angle xyz is equal to 90 degree.

  2. n = real depth / apparent depth is only an approximate rule

    Ya , I found some web sites they consider in a similar way with approximate symbol.

    [math]

    \approx ~

    [/math]

    Here I want the solution for this question as it seems to me that I've got the proof.

    Thank you

  3. I add some information I got from the net here.

    Bleach reacts with acid to give out greenish-yellow chlorine. Bleach also reacts with ammonia to form chloramine as you mentioned. It is a toxic gas which penetrate and injure the deep tissue of our lungs. They cannot be absorbed by the mucus lining on our respiratory tract (Can mucus lining on the tract absorb chlorine?) Then they turn back into HClO and NH3 and reacts with alveoli.

  4. I am not an American or an European.

    I found some grammar points in my book I think that helps you.

    "I'm going to the bank," said Mary---Correct

    "I'm going to the bank," said she ----wrong

    "I'm going to the bank," she said ----correct

    When the reporting clause comes after the quote, we can place the subject after the verb unnless the subject is a pronoun.

  5. Can anyone show me a proof of "refractive index= (real depth)\(apparent depth) "?

    I found the proof in my book has a mistakes and I found some contradicts to this equation.

    The book said used a pair of similar triangles to infer it but the triangles are not similar.

    Hope it helps you bring me out of the troubles.

  6. Neither A nor B is equal to 90 degree, so C must be 90 degree.

    Prove BC^2=ACxCD first, then you can prove the orginal one.

    There are two methods.

    (1)Extend BC to E where E is a point on the circumference.

    Since angle C=90 degree, then it must passes through the centre of the circle.

    So BC=CE, then you can prove it with Pyth. theorem.

    You may consider the two similar triangle, the ones like a butterfly.

    (2)Join BD, angle ABD=90 degree.

    You can see that ACxCD=BC^2.

     

    Either one of the two above leads you the answer.

  7. With copper and zinc electrode, copper(II) sulphate as electrolyte, what will be the product?

    My exercise book said that there will be a gas from the positive electrode (copper electrode).

    I checked the standard reduction potential and found that the oxidizing power of sulphate ion is smaller than that of copper (II) ion. so is my book wrong?

     

    And which anion has a smaller oxidizing power than copper (II) ion as well?

  8. My kitchen sink accumulated lots of fat and dirty water cannot be discharged.

    I tried to put some drain cleaner but it failed to remove the oil.

    It corrodes my kitchen sink instead of "eating" the oil. Eventually, I asked my parents' friend for help and the problem is solved.

    I learn lipase from pancreatic juice can digest the lipid into fatty acids and glycerol which is soluble in water. Moreover, bile salts in bile emulsify lipid into small oil droplets and aids the removal of it./

    Nevertheless, it is quite difficult for some normal civils to utilize them in this way.

    Anyone knows some reagent which aids me to get rid of these oil?

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