Let S1 = \z C : |z| 5\, S2 = \z C : Im ( z + 1 - 3 i1 - 3 i ) 0 \ and S3 = \z C : Re(z) 0\. Then the area of the region S1 S2 S3 is :
- 125 24
- 125 6
- 125 12
- 125 4
Answer
(3) 125 12
Solution
Put z = x + iy and multiply by 1 + 3i1 + 3i:
Im (x + 1 + i(y - 3))(1 + 3i)4 = 3(x + 1) + y - 34 = 3x + y4
S2: 3x + y 0 (on the side of the line y = - 3x containing (1, 0)); S3: x 0; S1: disc of radius 5
[figure]
the line makes 60 below the x-axis sector angle = 60 + 90 = 150 = 5 6
Area = 12r2 = 12 25 5 6 = 125 12
Answer: (3)