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If in ΔABC, secA, secB, secC are in harmonic progression, then 

(A) a, b, c, are in harmonic progression.

(B) cotA/2,cotB/2,cotC/2 are in harmonic progression

(C)  r1,r2,r3 are in arithmetic progression

(D)  cotA/2,cotB/2,cotC/2 are in arithmetic progression

1 Answer

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by (53.5k points)
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Best answer

Correct option (B), (C) 

Given cos A , cosB, cosC are in AP.

Then 2 cosB = cosA + cosC

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