In a $\triangle A B C$, if $r_1 r_2+r_3=35, r_2 r_3+r_1=63$ and $r_3 r_1+r_2=45$, then $2 s=$

$P Q R$ is an isosceles triangle with $P Q=P R$. If the radius of the circumcircle of $\triangle P Q R$ is equal to the length of $P Q$ then $\angle P=$

In an isosceles right angled triangle, a straight line is drawn from the mid-point of one of the equal sides to the opposite vertex. Then, a pair of possible values of the cotangents of the two angles so formed at that vertex are