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

If two adjacent sides of a cyclic quadrilateral are $2$ and $5$ and the angle between them is $60^{\circ}$. If the third side is $3$,then the remaining fourth side is :-

In a $\triangle ABC$,$2ac \sin \left(\frac{A-B+C}{2}\right)$ is equal to

In a $\triangle ABC$,$\operatorname{cosec} A(\sin B \cos C + \cos B \sin C)$ is equal to

In a $\triangle ABC$,the altitudes from $B$ and $C$ to the opposite sides are not shorter than their respective opposite sides. Then,one of the angles of $\triangle ABC$ is $........^{\circ}$

In a triangle $ABC,$ if $a \sin A = b \sin B,$ then the nature of the triangle is: