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 $H.P.$
The number of terms common to the two A.P.'s $3,7,11, \ldots ., 407$ and $2,9,16, \ldots . .709$ is
Find the sum of all natural numbers lying between $100$ and $1000,$ which are multiples of $5 .$
The number of terms in an $A .P.$ is even ; the sum of the odd terms in it is $24$ and that the even terms is $30$. If the last term exceeds the first term by $10\frac{1}{2}$ , then the number of terms in the $A.P.$ is
The ratio of the sums of first $n$ even numbers and $n$ odd numbers will be
If $\tan \left(\frac{\pi}{9}\right), x, \tan \left(\frac{7 \pi}{18}\right)$ are in arithmetic progression and $\tan \left(\frac{\pi}{9}\right), y, \tan \left(\frac{5 \pi}{18}\right)$ are also in arithmetic progression, then $|x-2 y|$ is equal to: