If the angles of a triangle $ABC$ are in $A.P.$,then

In a $\triangle ABC$,$\sin 2A + \sin 2B + \sin 2C =$

In a $\Delta ABC$,the expression $\frac{\cos C + \cos A}{c + a} + \frac{\cos B}{b}$ is equal to:

In a $\triangle ABC$,if $\angle A = 60^{\circ}$,then $(a+b+c)(b+c-a) =$

Given $\frac{b + c}{11} = \frac{c + a}{12} = \frac{a + b}{13}$ for a $\Delta ABC$ with usual notation. If $\frac{\cos A}{\alpha} = \frac{\cos B}{\beta} = \frac{\cos C}{\gamma}$,then the ordered triple $(\alpha, \beta, \gamma)$ is proportional to

In a triangle $ABC$ with usual notations,if $a, b, c$ are in arithmetic progression,then $\tan \frac{A}{2} \cdot \tan \frac{C}{2} =$