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Show that 1 + I10 + I20 + I30 is a Real Number.

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प्रश्न

Show that 1 + i10 + i20 + i30 is a real number.

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उत्तर

\[1 + i^{10} + i^{20} + i^{30} \]

\[ = 1 + i^{4 \times 2 + 2} + i^{4 \times 5} + i^{4 \times 7 + 2} \]

\[ = 1 + \left[ \left( i^4 \right)^2 \times i^2 \right] + \left( i^4 \right)^5 + \left[ \left( i^4 \right)^7 \times i^2 \right]\]

\[ = 1 + i^2 + 1 + i^2 \left( \because i^4 = 1 \right)\]

\[ = 1 - 1 + 1 - 1 \left( \because i^2 = - 1 \right)\]

\[ = 0\]

\[\text { This is a real number} . \]

\[\text { Hence proved } .\]

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अध्याय 13: Complex Numbers - Exercise 13.1 [पृष्ठ ४]

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आर.डी. शर्मा Mathematics [English] Class 11
अध्याय 13 Complex Numbers
Exercise 13.1 | Q 2 | पृष्ठ ४

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