Variable Definition and 1000 Threads

A variable star is a star whose brightness as seen from Earth (its apparent magnitude) fluctuates.
This variation may be caused by a change in emitted light or by something partly blocking the light, so variable stars are classified as either:

Intrinsic variables, whose luminosity actually changes; for example, because the star periodically swells and shrinks.
Extrinsic variables, whose apparent changes in brightness are due to changes in the amount of their light that can reach Earth; for example, because the star has an orbiting companion that sometimes eclipses it.Many, possibly most, stars have at least some variation in luminosity: the energy output of our Sun, for example, varies by about 0.1% over an 11-year solar cycle.

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  1. B

    Current-voltage relation for series association of variable capacitors

    Hello, I have an issue with the problem below. I have a series connection of two variable capacitances C_{1}(t) and C_{2}(t). I want to establish the differential equation between the current i and voltage V on the ports of the series connection. The capacitance of the series connection of...
  2. U

    Fluctuating Refractive Index and Light Perception

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  3. M

    How Do You Calculate P{S < t < S + R} for Independent Exponential Variables?

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  4. D

    MHB How can I use variable transformation to obtain a solution for this ODE?

    Given the following ODE \[ \left(\frac{du}{dx}\right)^2 = \mu u^2 - \frac{2\alpha}{\sigma + 2}u^{\sigma + 2} - \frac{\gamma}{\sigma + 1}u^{2(\sigma + 1)} \] How do I obtain \[ u(x) = \left(\frac{A}{B + \cosh(Dx)}\right)^{1/\sigma} \] where \(A = \frac{(2 + \sigma)B\mu}{\alpha}\), \(B =...
  5. R

    Strange Change of Variable of Integration

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  6. C

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  7. F

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  8. L

    Difference between a variable and a constant?

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  9. S

    Random Variable and Distribution Function Relationship

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  10. M

    What are the equations for conic sections in 4 dimensions?

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  11. A

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  12. W

    MHB Need Explanations For The Red Part (2 variable inequality)

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  13. R

    (Probability/Statistics) Transformation of Bivariate Random Variable

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  14. M

    Partial derivative that contains the independent variable as an deriva

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  15. N

    MHB Conditional PDF of this random variable

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  16. A

    An inequality for a two variable function

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  17. S

    MHB Dealing with 5 input variable Kmaps

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  18. P

    Generating level surface from 2 variable function

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  19. PsychonautQQ

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  20. G

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  21. BruceW

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  22. M

    Find E[(X-mu)^k] - Normal Random Variable

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  23. D

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  24. F

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  25. X

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  26. J

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  27. B

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  28. naima

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  29. T

    Variable Frequency Drive vs. Servo Drive

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  30. J

    Define the function of density of the random variable Y.

    We selected X point from interval (-1,2). If X=x, we selected point Y from (-1,x^2). Define the function of density of the random variable Y.
  31. Saitama

    Variable mass system - sand falling on flatcar

    Homework Statement A flatcar of mass ##m_0## starts moving to the right due to a constant horizontal force F. Sand spills on the flatcar from a stationary hopper. The velocity of loading is constant and equal to ##\mu## kg/s. Find the time dependence of the velocity and acceleration of flatcar...
  32. C

    Change of variable for 2nd partial differentiation and higher.

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  33. P

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  34. S

    MHB Derivative with respect to which variable?

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  35. M

    Inverse function of a two variable function

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  36. M

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  37. L

    Prove convergence in probability for n * Poisson variable to zero

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  38. G

    Differential Equation with Function of Shifted Variable

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  39. M

    Variable of an equation is in the denominator

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  40. O

    How to integral ? How can they ignore that variable?

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  41. E

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  42. Jeffack

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  43. I

    Jacobian Determinant/ mult. variable implicit differentiation

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  44. P

    Who first studied variable speed of light? - Einstein

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  45. C

    Covariance Matrix of a Vector Random Variable w/ Components Related

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  46. trash

    [Probability] Expected Value of Random Variable

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  47. H

    MHB PGF of a conditional random variable

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  48. K

    Question on variable definitions in Paschens law? (breakdown voltage)

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  49. A

    Magnitude of the tension when there is static (variable) friction

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  50. A

    I do not understand Variable density

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