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If a = cosθ + isinθ, find the value of aa1+a1-a. - Mathematics

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प्रश्न

If a = cosθ + isinθ, find the value of `(1 + "a")/(1 - "a")`.

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उत्तर

Given that: a = cosθ + isinθ

∴ `(1 + a)/(1 - a) = (1 + cos theta + i sin theta)/(1 - cos theta - i sin theta)`

= `(1 + cos theta + i sin theta)/(1 - cos theta - i sin theta) xx (1 - cos theta + i sin theta)/(1 - cos theta + i sin theta)`

= `(1 - cos theta + i sin theta + cos theta - cos^2 theta + i sin theta cos theta + i sin theta - i sin theta cos theta + i^2 sin^2 theta)/((1 - cos theta)^2 - i^2 sin^2 theta)`

= `(1 + i sin theta - cos^2 theta + i sin theta - sin^2 theta)/(1 + cos^2 theta - 2 cos theta + sin^2 theta)`

= `(sin^2 theta + 2i sin theta - sin^2 theta)/(1 + 1 - 2 cos theta)`

= `(2i sin theta)/(2 - 2 cos theta)`

= `(2i sin theta)/(2(1 - cos theta))`

= `(i sin theta)/(1 - cos theta)`

= `(2 sin  theta/2 cos  theta/2.i)/(2sin^2  theta/2)`

= `cot  theta/2 . i`

Hence, `(1 + a)/(1 - a) = icot  theta/2`.

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अध्याय 5: Complex Numbers and Quadratic Equations - Exercise [पृष्ठ ९१]

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एनसीईआरटी एक्झांप्लर Mathematics [English] Class 11
अध्याय 5 Complex Numbers and Quadratic Equations
Exercise | Q 6 | पृष्ठ ९१

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