हिंदी

Which of the following is correct for any two complex numbers z1 and z2?

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प्रश्न

Which of the following is correct for any two complex numbers z1 and z2?

विकल्प

  • |z1z2| = |z1||z2|

  • arg(z1z2) = arg(z1).arg(z2)

  • |z1 + z2| = |z1| + |z2|

  • |z1 + z2| ≥ |z1| – |z2|

MCQ
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उत्तर

|z1z2| = |z1||z2|

Explanation:

Let z1 = r1(cosθ1 + isinθ1)

∴ |z2| = r1

And z2 = r2(cosθ2 + isinθ2)

∴ |z2| = r

z1z2 = r1(cosθ1 + isinθ1).r2(cosθ2 + isinθ2)

= r1r2(cosθ1 + isinθ1).(cosθ2 + isinθ2)

= r1r2(cosθ1 cosθ2 + isinθ2 cosθ1 + isinθ1 cosθ2 + i2sinθ1 sinθ2)

= r1r2 [(cosθ1 cosθ2 – sinθ1 sinθ2) + i(sinθ1 cosθ2 + cosθ1 sinθ2)]

= r1r2 [cos(θ1 + θ2) + isin(θ1 + θ2)]

∴ |z1z2| = |z1||z2|

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अध्याय 5: Complex Numbers and Quadratic Equations - Exercise [पृष्ठ ९६]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
अध्याय 5 Complex Numbers and Quadratic Equations
Exercise | Q 41 | पृष्ठ ९६

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