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महाराष्ट्र राज्य शिक्षण मंडळएचएससी विज्ञान (सामान्य) इयत्ता ११ वी

Find the modulus and amplitude of the following complex numbers. (1 + 2i)2 (1 − i)

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प्रश्न

Find the modulus and amplitude of the following complex numbers.

(1 + 2i)2 (1 − i)

बेरीज
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उत्तर

Let z = (1 + 2i)2 (1 − i)

= (1 + 4i + 4i2) (1 − i)

= [1 + 4i + 4(−1)] (1 − i) ...[∵ i2 = −1]

= (−3 + 4i) (1 − i)

= −3 + 3i + 4i − 4i2

= −3 + 7i − 4 (−1)

= − 3 + 7i + 4

∴ z = 1 + 7i

∴ a = 1, b = 7, i. e. a > 0, b > 0

∴ |z| = `sqrt("a"^2 + "b"^2)`

= `sqrt(1^2 + 7^2)`

= `sqrt(1 + 49)`

= `5sqrt(2)`

Here, (1, 7) lies in 1st quadrant

amp (z) = `tan^-1("b"/"a")`

= tan–1(7)

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पाठ 1: Complex Numbers - Exercise 1.3 [पृष्ठ १५]

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