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Studying Rudin's Principles of Mathematical Analysis Through ...

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1.6. THE COMPLEX FIELD 9<br />

1.6.6 Theorem: (a, b) = a + bi<br />

Prove that if a, b ∈ R, (a, b) = a + bi.<br />

1.6.7 Definition: z, Re[z], Im[z]<br />

What are<br />

Conjugate<br />

Real part,<br />

Imaginary part <strong>of</strong> z?<br />

1.6.8 Theorem<br />

If z and w are complex, prove that<br />

(a) z + w = z + w<br />

(b) zw = z · w<br />

(c) z + z = 2Re(z), z − z = 2iIm(z)<br />

(d) zz ≥ 0 and real.<br />

1.6.9 Definition<br />

What is absolute value <strong>of</strong> a complex<br />

number z?<br />

1.6.10 Theorem<br />

Let z and w be complex numbers.<br />

Prove that<br />

(a) |z| > 0 unless z = 0, |0| = 0<br />

(b) |z| = |z|<br />

(c) |zw| = |z||w|<br />

(d) |Rez| ≤ |z|<br />

(e) |z + w| ≤ |z| + |w|<br />

1.6.11 Notation<br />

What is the summation notation?<br />

1.6.12 Theorem: Schwartz Inequality<br />

What is the Schwartz inequality?<br />

State and prove it for complex numbers.

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