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

Which of the following sets of data does not uniquely determine an acute-angled $\Delta ABC$ ($R$ = circum-radius)?

If the sides of a triangle are in the ratio $2 : \sqrt{6} : (\sqrt{3} + 1)$,then the largest angle of the triangle will be.....$^o$

If in a $\Delta ABC$,$a, b, c$ are in $A.P.$,then $\tan \frac{A}{2} \tan \frac{C}{2} = $

In $\triangle ABC$,the sum of the lengths of two sides is $x$ and the product of those lengths is $y$. If $c$ is the length of the third side and $x^2 - c^2 = y$,then the circumradius of the triangle is

If $a = 2 \sqrt{2}$, $b = 6$, and $A = 45^{\circ}$, then: