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# Modulus and argument of complex number

### Modulus and argument of complex number (Question)

1. Determine the modulus and argument of 10 + 5i.
2. Express 10 + 5i in the form of r(cos a + sin a*i)

Guide:

|a + bi| = r = √(a2 + b2)
Argument of the complex number = tan-1(b/a)

Argument form of a complex number
x + yi = r(cos a + sin a*i)

### Modulus and argument of complex number (Answer)

1. Modulus = √125, Argument = 0.464rad
2. 10 + 5i = √125(cos 0.464rad + sin0.464rad*i)

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