If `a, b, c` are in `H.P.,` then `4^(-a^-1),4^(-b^-1),4^(-c^-1)` are in

If a, b, c are in H.P then ((1)/(b) + (1)/(c )-(1)/(a)) ((1)/(c ) + (1)/(a) - (1)/(b)) =

If a,b,c are in A.P and b,c,a are in H.P then a^(4) =

If a,b,c are in H.P., then the value of ((1)/(b)+(1)/(c)-(1)/(a))((1)/(c)+(1)/(a)-(1)/(b)) is

If a,b,c are in H.P., then the value of ((1)/(b)+(1)/(c)-(1)/(a))((1)/(a)+(1)/(b)-(1)/(c)) is

Lengths of the tangents from A,B and C to the incircle are in A.P., then (a) r_(1), r_(2), r_(3) are in H.P (b) r_(1), r_(2), r_(3) are in A.P (c)a, b, c are in A.P (d) cos A = (4c -3b)/(2c)