  # caseclosed

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Meson
1. This is from the book, need help changing it into mathematical model. "Consider a tank used for certain hydrodynamic experiments. After one experiment the tank contains 200 litres of a dye solution with a concentration of 1 g/litre. To prepare for the next experiment, the tank is rinsed with fresh water flowing in at a rate of 2 litres/min, the well-stirred solution flowing out at the same rate. Find the time that will elapse before the concentration of dye in the tank readches 1% of its original value."
2. ok, I have claried this, apprarently it was for angle between 2 planes... grr those conventional ways
3. $\int{\sec{x}^3dx}=F$ $u=Sec(x)$ $du=Sec(x)Tan(x)dx$ $dv=Sec(x)^2dx$ $v=Tan(x)$ $F=$$Sec(x)Tan(x)$ $\int{\tan{x}^2sec{x}dx}$ $F=$$Tan(x)^2=Sec(x)^2-1$ $F=$$Sec(x)Tan(x)$ $-\int{\sec{x}^3dx}$$+\int{sec{x}dx}$ $F=$$Sec(x)Tan(x)$ $-F$$+ln(sec(x)+tan(x))$ $2F=$$Sec(x)Tan(x)$ $+ln(sec(x)+tan(x))$ $F=$$(Sec(x)Tan(x))/2$ $+(ln(sec(x)+tan(x))/2$ thank you very much for giving me the hint. I so forgot how to do this.
4. well, I just did the questions in the book and my professor's method doesn't match the answer in the book. He says the book is wrong...... the book is Thomas's Calculus 11th edition. also I see nowhere online where it says absolute value of dot product.
5. cos(theta)= (A.B)/(lAllBl) OR cos(theta)=(lA.Bl)/(lAllBl) ---->my teacher insist this one is right and other one is wrong
6. ok, that's why... I should just leave it as sec^3 instead of changing using trig indentity. thank you very much.
7. yes, I tried setting u=(x^2+1)^(1/2) and dv=dx but I am not getting any log in the answer which means wrong. using the parts on sec(theta)^3 gets me nowhere, I change to (tan(x)^2+1)sec(x) and then set u=tan(x)^2 and dv=sec(x) dx which lead me to very complicated. I know I did this before but I don't remember how I did it.
8. integrate (1+x^2)^(1/2) I used trig substitution and gotten integrate sec(theta)^3 but no clue what to do ....
9. find the point of intersection of the lines x=2t+1, y=3t+2, z=4t+3, and x=s+2, y=2s+4, z=-4s-1, and the find the plane determined by these lines. I don't know what to do...
10. oh, because it looks like the Calculus 2 stuff I did this year, thats why I was wondering.
11. so what grade are you in since you are doing this?
12. how to differentiate sin(x)^x for 0<x<pi/2
13. ok, now I understand it, basically constant can be thrown out.
14. I see, I hope the exam does not give mathematica answer as the chice because I have absolutely no clue how to get sec(x)^2/2, anyone know how to get that?
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