The angles of a triangle are in the ratio $1:3:5$. Find the greatest angle. (in $\pi /9$)

In a triangle $ABC$,$s\left[\frac{r_1-r}{a}+\frac{r_2-r}{b}+\frac{r_3-r}{c}\right]=$

In a triangle,the lengths of the sides are integers. Suppose that the length of one side is $1$,and the longest altitude is twice the shortest altitude. Let $R$ and $r$ be the circumradius and inradius of the triangle,respectively. If $R:r = m:n$,where $m$ and $n$ are coprime positive integers,then $m + n$ is

If the lengths of the sides of a triangle are $3, 5, 7$,then the largest angle of the triangle is

If the area of triangle $ABC$ is $b^2-(c-a)^2$,then $\tan B=$

In a $\triangle ABC$,the sides $a, b, c$ are in $A$.$P$. if and only if $r_1, r_2, r_3$ are in