The area of an isosceles triangle is $9 \, cm^2$. If the equal sides are $6 \, cm$ in length,the angle between them is .... $^\circ$.

In $\Delta ABC$,$8 \Delta = (b + c)(bc + 1)$,then the circumradius of $\Delta ABC$ is (where $\Delta$ denotes the area of the triangle and $b, c$ are the lengths of sides $AC$ and $AB$ respectively):

The perimeter of a $\Delta ABC$ is $6$ times the arithmetic mean of the sines of its angles. If the side $a$ is $1$,then the angle $A$ is

In a $\triangle ABC$,if $a+3b=3c$,then $\sin \frac{A}{2} =$

In a triangle $ABC$ with usual notations,if $\tan \left(\frac{B-C}{2}\right) = x \cot \frac{A}{2}$,then $x =$

In $\triangle ABC$,with usual notations,if $\frac{1}{b+c}+\frac{1}{c+a}=\frac{3}{a+b+c}$,then $m \angle C$ is equal to