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Sinx + icos2x and cosx – isin2x are conjugate to each other for ______. - Mathematics

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प्रश्न

sinx + icos2x and cosx – isin2x are conjugate to each other for ______.

विकल्प

  • x = nπ

  • x = `(n + 1/2) pi/2`

  • x = 0

  • No value of x

MCQ
रिक्त स्थान भरें

उत्तर

sinx + icos2x and cosx – isin2x are conjugate to each other for x = 0.

Explanation:

Let z = sinx + icos2x

`barz` = sinx – icos2x

But we are given that `barz` = cosx – isin2x

∴ sinx – icos2x = cosx – isin2x

Comparing the real and imaginary parts, we get

sinx = cosx and cos2x = sin2x

⇒ tanx = 1 and tan2x = 1

⇒ tanx = `tan  pi/4` and  tan2x = `pi/4`

∴ x = `npi + pi/4`, n ∈ I and 2x = `npi + pi/4`

⇒ x = 2x

⇒ 2x – x = 0

⇒ x = 0

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अध्याय 5: Complex Numbers and Quadratic Equations - Exercise [पृष्ठ ९५]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
अध्याय 5 Complex Numbers and Quadratic Equations
Exercise | Q 35 | पृष्ठ ९५

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