Recent content by Donaldos

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    Linear transformation: Rotations in R3

    You need to find the two other rotation matrices using the exact same method. The standard matrix for T is found by simply multiplying the three matrices together.
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    Integral of trigonometric functions

    You can use the following identity: \sin a \sin b=\frac{\cos(a-b)-\cos(a+b)} 2
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    Calculating the Arc Length of y=e^x from 0 to 1

    u=\sqrt{1+e^{2x}} {\rm d}u=\frac{e^{2x}}{\sqrt{1+e^{2x}}}=\frac{u^2-1}{u} {\rm{d}x} and s={\int\limits_{\sqrt{2}}^{\sqrt{1+e^2^}}} {\frac{u^2}{u^2-1^}} \quad {\rm d}u ?
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    How Do You Calculate the Electric Field Between a Wire and a Cylinder?

    Let \lambda be the linear charge distribution in the wire. Use Gauss's Law to express the electric field in terms of r and \lambda. Then use this: to determine the expression of \lambda as a function of V.
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    A group that's a collection of sets

    Show that A*B=B*A. Find I \in S such that A*I=I*A=A , \quad\forall A \in P. Find B \in S such that A*B=I .
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    What is the determinant of this 5x5 matrix and how can it be calculated?

    Your last determinant should be \left|\begin{array}{cc} -18 & 1\\ -50 &9\end{array}\right| not \left|\begin{array}{cc} -18 & 0\\ -50 &9\end{array}\right|
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    What is the determinant of this 5x5 matrix and how can it be calculated?

    The third line of your second determinant is incorrect.
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    Linear Algebra- Kernel and images of a matrix

    In other words, we have \ker(A)\subset \ker(A^2). Yes. You could also write : \operatorname{im}(A^2)\subset \operatorname{im}(A) Now, how can you apply this to \ker(A^3), \ker(A^4)... and \operatorname{im}(A^3), \operatorname{im}(A^4)...?
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    Linear Algebra- Kernel and images of a matrix

    a. If x \in \ker(A), what can you say about A^2 x? What does that tell you about \ker(A^2)? b. For any x, A^2x is in \operatorname{im}(A^2). If you rewrite A^2x as A(Ax)=Ay, what can you say about \operatorname{im}(A)?
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    Gravitational and electric fields

    Where did that expression come from? Find an expression for the radial acceleration in terms of the orbital speed and R. Then use Newton's second law.
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    Integrating arcsin: Solving \int \sqrt{9-x^{2}}dx with step-by-step explanation

    \int \frac{{\rm d}u}{\sqrt{1-u^2}}=\arcsin u but here we have \int \frac{{\rm d}x}{\sqrt{1-\left(\frac x 3 \right)^2}} u= \frac x 3 \Rightarrow {\rm d}x= ?
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    A couple of Integration problems

    1. Decompose \frac{1}{x\left(x^4+8\right)} into partial fractions 2. u=\sqrt{x} + partial fraction decomposition
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    How do I convert f(x) into its Fourier Transform?

    All you need is the following property: \int\limits_{-\infty}^{+\infty} f(x)\delta\left(x-a\right)=f(a)
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