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chaoseverlasting
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Can someone explain the De Moivre's Theorem and how its used to evaluate integrals of the type [tex]\int sin^mxcos^nxdx[/tex]
Gib Z said:You can use Identites such as [tex]\cos^4 x = \frac{\cos 4x + 4\cos 2x +3}{8}[/tex] which can be derived from expanding the LHS of the theorem, to make the integrals easy.
Gib Z said:De Moivre's Theorem:
[tex](\cos x + i \sin x)^n = \cos nx + i \sin nx[/tex]
Proof by induction or Euler's Formula.
Explain it? There it is, no intuitive feel or understanding about it, not unless you're Gauss.
matt grime said:Really? I beg to differ.
Raising a complex number of modulus 1 to the n'th power multiplies the argument by n. It is saying that multiplication of (unit) complex numbers gives rotations of the complex plane.
matt grime said:Really? I beg to differ.
Raising a complex number of modulus 1 to the n'th power multiplies the argument by n. It is saying that multiplication of (unit) complex numbers gives rotations of the complex plane.
De Moivre's Theorem is a mathematical formula that relates complex numbers to trigonometric functions. It states that for any complex number z = r(cos θ + isin θ), where r is the modulus (or absolute value) and θ is the argument (or angle), the nth power of z can be expressed as z^n = r^n(cos nθ + isin nθ).
De Moivre's Theorem allows us to express the integral of sin^m(x)cos^n(x) as a combination of trigonometric functions. By using the binomial theorem to expand (sin x + cos x)^m+n, we can then use the theorem to simplify the resulting expression. This allows us to solve integrals involving powers of sin x and cos x.
De Moivre's Theorem has many practical applications in fields such as physics, engineering, and signal processing. It is used to simplify complex calculations involving trigonometric functions, and can also be used to solve differential equations and describe periodic phenomena.
Euler's formula is a special case of De Moivre's Theorem, where the complex number z = 1. In this case, the formula becomes e^ix = cos x + isin x, which is a fundamental relationship between exponential and trigonometric functions.
De Moivre's Theorem is limited to dealing with powers of complex numbers and trigonometric functions. It cannot be used to solve integrals involving other types of functions, such as logarithmic or exponential functions. Additionally, it is only applicable to integrals with finite limits of integration.