In $\Delta ABC$, if $a, b, c$ are in $A.P.$ (with usual notations), identify the incorrect statements -
$h_1, h_2, h_3$ are in $H.P.$, where $h_1, h_2, h_3$ are altitudes from vertices $A,B$ $C$ respectively.
$sinA, sinB, sinC$ are in $A.P.$
$r_1, r_2, r_3$ are in $A.P.$
$tan \frac{A}{2} , tan \frac{B}{2}, tan \frac{C}{2} $ are in $H.P.$
If the sum of the first $n$ terms of a series be $5{n^2} + 2n$, then its second term is
If ${S_1},\;{S_2},\;{S_3},...........{S_m}$ are the sums of $n$ terms of $m$ $A.P.'s$ whose first terms are $1,\;2,\;3,\;...............,m$ and common differences are $1,\;3,\;5,\;...........2m - 1$ respectively, then ${S_1} + {S_2} + {S_3} + .......{S_m} = $
What is the sum of all two digit numbers which give a remainder of $4$ when divided by $6$ ?
The sum of the first $20$ terms common between the series $3 +7 + 1 1 + 15+ ... ......$ and $1 +6+ 11 + 16+ ......$, is