{"id":6520,"date":"2021-10-17T22:02:30","date_gmt":"2021-10-17T16:32:30","guid":{"rendered":"https:\/\/mathemerize.com\/?p=6520"},"modified":"2021-11-21T18:12:29","modified_gmt":"2021-11-21T12:42:29","slug":"how-to-find-the-reciprocal-of-a-complex-number","status":"publish","type":"post","link":"https:\/\/mathemerize.com\/how-to-find-the-reciprocal-of-a-complex-number\/","title":{"rendered":"How to Find the Reciprocal of a Complex Number"},"content":{"rendered":"
Here you will learn how to find the reciprocal of a complex number with examples.<\/p>\n
Let’s begin – <\/p>\n
The reciprocal is also called multiplicative inverse.<\/p>\n
Let z = a + ib be a non-zero complex number. Then<\/p>\n
\\(1\\over z\\) = \\(1\\over a + ib\\)<\/p>\n
Multiply numerator and denominator by conjugate of denominator,<\/p>\n
\\(1\\over z\\) = \\(1\\over a + ib\\) \\(\\times\\) \\(a – ib\\over a – ib\\)<\/p>\n
\\(\\implies\\) \\(1\\over z\\) = \\(a – ib\\over a^2 – i^2b^2\\) = \\(a – ib\\over a^2 + b^2\\)<\/p>\n
\\(\\implies\\) \\(1\\over z\\) = \\(a\\over a^2 + b^2\\) + \\(i(-b)\\over a^2 + b^2\\)<\/p>\n
Clearly, \\(1\\over z\\) is equal to the multiplicatve inverse of z.<\/p>\n
Also, \\(1\\over z\\) = \\(a – ib\\over a^2 + b^2\\) = \\( \\bar{z}\\over | z |^2\\)<\/p>\n
Thus, the multiplicative inverse of a non-zero complex number is same as its reciprocal and is given by<\/p>\n
\n\\(Re (z)\\over | z |^2\\) + \\(i{(-Im (z))\\over | z |^2}\\) = \\( \\bar{z}\\over | z |^2\\)<\/p>\n<\/blockquote>\n
Example<\/strong><\/span> : Find the reciprocal or multiplicative inverse of the following complex numbers.<\/p>\n
(i) 3 + 2i<\/p>\n
(ii) \\((2 + \\sqrt{3}i)^2\\)<\/p>\n
Solution<\/span><\/strong> :<\/p>\n
(i) Let z = 3 + 2i. Then,<\/p>\n
\\(1\\over z\\) = \\(1\\over 3 + 2i\\)<\/p>\n
= \\(3 – 2i\\over (3 + 2i)(3 – 2i)\\) = \\(3 – 2i\\over 9 – 4i^2\\)<\/p>\n
= \\({3\\over 13} – {2\\over 13}i\\)<\/p>\n
(ii) Let z = \\((2 + \\sqrt{3}i)^2\\). Then,<\/p>\n
z = \\(4 + 3i^2 + 4\\sqrt{3}i\\)<\/p>\n
= \\(4 – 3 + 4\\sqrt{3}i\\) = \\(1 + 4\\sqrt{3}i\\)<\/p>\n
\\(\\therefore\\) \\(1\\over z\\) = \\(1\\over 1 + 4\\sqrt{3}i\\)<\/p>\n
Multiply numerator and denominator by conjugate of denominator<\/p>\n
\\(\\implies\\) \\(1\\over z\\) = \\(1 – 4\\sqrt{3}i\\over (1 + 4\\sqrt{3}i)(1 + 4\\sqrt{3}i)\\)<\/p>\n
= \\(1 – 4\\sqrt{3}i\\over 1 + 48\\) = \\(1\\over 49\\) – \\(4\\sqrt{3}i\\over 49\\)<\/p>\n\n\n