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  1. Home
  2. 12th grade
  3. Algebra II
  4. Exercise : Find the magnitude (or absolute value) of a complex number

Find the magnitude (or absolute value) of a complex number Algebra II

Find the magnitude (or absolute value) of the following complex number.

z=3-2i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of 3-2i equals:

\sqrt{3 ^ 2 + \left(- 2\right) ^ {2}}=\sqrt{9+4}=\sqrt{13}

\left| 3-2i \right|=\sqrt{13}

z = 3+4i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of 3+4i equals:

\sqrt {3 ^ 2 + 4 ^ {2}} = \sqrt {9 + 16} = \sqrt {25}=5

\left | 3+4i \right | = 5

z=1+7i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of 1 + 7i equals:

\sqrt {1 ^ 2 + 7 ^ {2}} = \sqrt {1 + 49} = \sqrt {50}=\sqrt{25} \cdot \sqrt{2}=5\sqrt{2}

\left | 1 + 7i \right | = 5\sqrt {2}

z=-3-6i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of -3 -6i equals:

\sqrt {\left(-3\right) ^ 2 + \left(-6\right) ^ {2}} = \sqrt {9 + 36} = \sqrt {45}=\sqrt{9} \cdot \sqrt{5}=3\sqrt{5}

\left | -3 -6i \right | = 3 \sqrt {5}

z=11i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of 7i equals:

\sqrt {0^ 2 + 7^ {2}} = \sqrt {49} =7

\left | 7i \right | = 7

z-5+8i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of -5+8i equals:

\sqrt {\left(-5\right) ^ 2 + 8 ^ {2}} = \sqrt {25+64}=\sqrt{89}

\left | -5+8i \right | = \sqrt{89}

z=1-i

Let z be a complex number such that:

z=a+ib

Then the magnitude of z is:

\left| z \right|=\sqrt{a^2+b^2}

Therefore, the magnitude of 1-i equals:

\sqrt {1 ^ 2 + \left(-1\right) ^ {2}} = \sqrt {2}

\left | 1-i \right | = \sqrt{2}

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See also
  • Course : Complex numbers
  • Exercise : Multiply complex numbers
  • Exercise : Divide complex numbers
  • Exercise : Match points of the complex plan and complex numbers
  • Exercise : Find the complex roots of a quadratic using the discriminant
  • Exercise : Convert between any forms of complex numbers
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