Complex Numbers 4 Question 2

2. A particle P starts from the point z0=1+2i, where i=1. It moves first horizontally away from origin by 5 units and then vertically away from origin by 3 units to reach a point z1. From z1 the particle moves 2 units in the direction of the vector i^+j^ and then it moves through an angle π2 in anti-clockwise direction on a circle with centre at origin, to reach a point z2. The point z2 is given by

(2008, 3M)

(a) 6+7i

(b) 7+6i

(c) 7+6i

(d) 6+7i

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Answer:

Correct Answer: 2. (d)

Solution:

z2=(6+2cos45,5+2sin45)=(7,6)=7+6i

By rotation about (0,0),

z2z2=eiπ/2z2=z2eiπ2=(7+6i)cosπ2+isinπ2=(7+6i)(i)=6+7i



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