In each of the cases below, determine whether the set U; is open or not, and briefly justify your answers: (i) U1 = {z € C; |z| <1 and |z– 1|<1 and |z- i| < 1} (ii) U2 = {z € C; Re z > 0} (iii) U3 = {z E C; Im z > 0}n{z € C; |z + 10i| < 2}

Advanced Engineering Mathematics
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ISBN:9780470458365
Author:Erwin Kreyszig
Publisher:Erwin Kreyszig
Chapter2: Second-order Linear Odes
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In each of the cases below, determine whether the set U; is open or not, and briefly
justify your answers:
(i)
U1 = {z € C; |z| <1 and |z– 1|<1 and |z- i| < 1}
(ii)
U2 = {z € C; Re z > 0}
(iii)
U3 = {z E C; Im z > 0}n{z € C; |z + 10i| < 2}
Transcribed Image Text:In each of the cases below, determine whether the set U; is open or not, and briefly justify your answers: (i) U1 = {z € C; |z| <1 and |z– 1|<1 and |z- i| < 1} (ii) U2 = {z € C; Re z > 0} (iii) U3 = {z E C; Im z > 0}n{z € C; |z + 10i| < 2}
Expert Solution
Step 1

(i)

The given set is U1=z; z<1 and z-1<1 and z-i<1. Define:

                                                 O1=z: z<1O2=z: z-1<1O3=z: z-i<1

Clearly U1=O1O2O3.

The set O1 is an open disc with radius 1 unit, centered at z=0 and hence open set. 

The set O2 is an open disc with radius 1 unit, centered at z=1 and hence open set. 

The set O3 is an open disc with radius 1 unit, centered at z=i and hence open set. 

Since finite intersection of open set is open in . Therefore U1=z; z<1 and z-1<1 and z-i<1, is an open set.

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