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B
2√(1−x2)(1+y2)(1−z2)
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C
2√(1+x2)(1+y2)(1+z2)
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D
2√(1−x2)(1+y2)(1+z2)
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Solution
The correct option is D2√(1+x2)(1+y2)(1+z2) Let x=tanA2y=tanB2 and z=tanC2. Where A+B+C=π. Thence tanA2.tanB2+tanB2.tanC2+tanC2tanA2=1 .... (property). Now x1+x2+y1+y2+z1+z2 =tan(A2)1+tan2(A2)+tan(B2)1+tan2(B2)+tan(C2)1+tan2(C2) =12[sinA+sinB+sinC] =12[4cosC2.cosB2.cosA2] =2cosC2.cosB2.cosA2 =2√(1+tanA2)2(1+tanB2)2(1+tanC2)2 =2√(1+x2)(1+y2)(1+z2)