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Show that the complex number z, satisfying the condition arg(z-1z+1)=π4 lies on a circle. - Mathematics

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प्रश्न

Show that the complex number z, satisfying the condition arg`((z - 1)/(z + 1)) = pi/4` lies on a circle.

योग

उत्तर

Let z = x + iy

Given that: arg`((z - 1)/(z + 1)) = pi/4`

⇒ arg(z – 1) – arg(z + 1) = `pi/4`  ......`[because "arg"(z_1) - "arg" (z_2) = "arg"z_1/z_2]`

⇒ arg[x + iy – 1] – arg[x + iy + 1] = `pi/4`  

⇒ arg[(x – 1) + iy] – arg[(x + 1) + iy] = `pi/4`

⇒ `tan^-1  y/(x - 1) - tan^-1  y/(x + 1) = pi/4`  ......`[because "arg" (x + yi) = tan^-1  y/x]`

⇒ `tan^-1  ((y/(x - 1) - y/(x + 1))/(1 + y/(x - 1) xx y/(x + 1))) = pi/4`

⇒ `(xy + y - xy + y)/(x^2 - 1 + y^2) = tan  pi/4`

⇒ `(2y)/(x^2 + y^2 - 1)` = 1

⇒ x2 + y2  – 1 = 2y

⇒ x2  + y2  – 2y – 1 = 0

Which is a circle.

Hence, z lies on a circle.

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  क्या इस प्रश्न या उत्तर में कोई त्रुटि है?
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 10 | पृष्ठ ९१

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