If x + 1 2 x 3 + x = A x + B x + C x 2 + 1 ,   then   cosec 1 1 A + cot - 1 1 B + sec - 1 C =
(a) 0         (b) π 2              (c) 5 π 6               (d) π 6

x+12x3+x=Ax+Bx+Cx2+1x+12xx2+1=Ax+Bx+Cx2+1x+12=xx2+1Ax+xx2+1Bx+Cx2+1x+12=Ax2+1+xBx+CPut x=012=AA=1x+12=x2+1+xBx+Cx2+1+2x=x2+1+xBx+C2x=xBx+C2x=Bx2+CxComparing both sidesB=0C=2cosec-11A+cot-11B+sec-1C=cosec-111+cot-110+sec-12=cosec-111+cot-1+sec-12=π2+0+π3=5π6

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