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  1. D

    Geometry problem

    Thanks for making an effort! It's always rewarding even if we don't solve exactly everything :)
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    Geometry problem

    Use the green triangle how? I don't know the short side or the hypothenus of it. I can't know how to aim the angle to the zero point 'inside' the mountain...
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    Geometry problem

    I would very much like you to explain this in detail (with drawings). Else I'm not quite sure I understand your method :P
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    Geometry problem

    No, it's not that easy unfortunatel. I don't know the distance to the zero point. In fact, I don't know any distances at all. Only the height of the two mountains. And the point was to use angles along with the mountain heights to solve the problem...
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    Geometry problem

    The point of the problem is this: Let's say you outside taking a hike somewhere. You can see the summit of to mountains (which you know the height of), and you're wondering how high above sea-level you are right now. The only tools you have is some kind of instrument making you able to measure...
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    Geometry problem

    I'm sorry. You're confusing me...
  7. D

    Geometry problem

    I'm leaning towards there not being a solution. However, if you perform two measurements, with the distance between measuring points known, the angles could tell you the distance to either mountain. Then it would be possible!
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    Geometry problem

    I can measure the angle between top A and B, but that's about it. I don't know any other length in that triangle. So I would say no. But I'm not sure...
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    Geometry problem

    Homework Statement I want to know if the problem needs another variable, or if it is possible to solve as it is. Homework Equations See figure in image included: You are a point x, some height h above zero-level. The two mountains have known height 500m and 400m. But you don't know how far...
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    Exponential equation - how to use ln?

    Aha! So i get a simple second degree equation: 64x^{2}-50x+4=0 Thanks :) But I'm thinking now that these numbers were 'convenient'...are there other ways to solve this if the numbers don't play along this nicely?
  11. D

    Exponential equation - how to use ln?

    Homework Statement Problem: find t in the following equation Homework Equations 64000e^{-1600t}+4000e^{-400t}=50000e^{-1000t} The Attempt at a Solution I know the answer: t=6.17\cdot\;10^{-4}s. But I'm struggling with how to get there. This is my attempt: Factorizing down to...
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    Height of a mountain

    I apologize if this problem is more of a math- than a physics problem. At least it is applicable in real life :) You are standing on some mountain and in your view are two other mountains, A and B. Also you can see the ocean as a referance zero point. The height of both mountains A and B are...
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    Integral of 1/1+sqrt(x)

    Ah, yes. That is much easier :) Thanks
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    Integral of 1/1+sqrt(x)

    Nevermind. I did it now. It was a simple mistake on my part. The integral should look like: \int_0^1{\frac{2u}{1+u}du} after substitution and then it should be calculated with integration by parts from there.
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    Integral of 1/1+sqrt(x)

    I'm having trouble calculating an integral: \int_0^1{\frac{1}{1+\sqrt{x}}dx} I decided to do a substitution: u=\sqrt{x} du=\frac{1}{2\sqrt{x}}dx=\frac{1}{2u}dx thus making the integral look like this: \int_0^1{\frac{1}{2u}\cdot\frac{1}{1+u}du} I transformed this integral to...
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    First order DE with exponential

    Thank you very much!
  17. D

    First order DE with exponential

    I want to solve a first order differential equation on the form y'+y=e^{x} I want to separate the variables, but not sure how...Thanks!
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    First order DE separable

    I have tried to solve the differential equation y'=x\sqrt{y} like this: y^{-\frac{1}{2}}y'=x \int{y^{-\frac{1}{2}}}dy=\int{xdx} y^{\frac{1}{2}}=\frac{x^2 +C}{4} y=\left(\frac{x^2+C}{4}\right)^2 Is this the right way to solve it? Because the answer in my textbook says that the...
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    Exponential function problem

    Thanks!
  20. D

    Exponential function problem

    I have a problem with an exponential function. I am wondering if an exact solution is possible, or if I have to write the solution as a logarithm of an unknown. A formula says that E(z)=E(0)^{-kz}, where E is light intensity and z is depth in water. My objective is to find the constant k. I...
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    Differential equation (to solve analytically)

    (x^2+1)y'=x^2+x-1+4xy How can I solve this equation analytically? I have almost no idea. I thought that y might be a series...please help :) Homework Statement Homework Equations The Attempt at a Solution
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