Question

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

Answer 1

Correct option (B), (C) 

Given cos A , cosB, cosC are in AP.

Then 2 cosB = cosA + cosC