Circle 2 Question 17

18. If P is a point of C1 and Q is a point on C2, then PA2+PB2+PC2+PD2QA2+QB2+QC2+QD2 is equal to

(a) 0.75

(b) 1.25

(c) 1

(d) 0.5

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Solution:

  1. Let the, equation of circles are

C1:(x1)2+(y1)2=(1)2

and C2:(x1)2+(y1)2=(2)2

Coordinates of P(1+cosθ,1+sinθ)

 and Q(1+2cosθ,1+2sinθ)PA2+PB2+PC2+PD2=(1+cosθ)2+(1+sinθ)2+(cosθ1)2+(1+sinθ)2+(cosθ1)2+(sinθ1)2+(1+cosθ)2+(sinθ1)2=12

Similarly, QA2+QB2+QC2+QD2=16

ΣPA2ΣQA2=1216=0.75



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