If the lines $x + 3y = 4$,$3x + y = 4$,and $x + y = 0$ form a triangle,then the triangle is:

Let $PQR$ be a triangle in which $PQ=3$. From the vertex $R$,draw the altitude $RS$ to meet $PQ$ at $S$. Assume that $RS=\sqrt{3}$ and $PS=QR$. Then,$PR$ equals

The sides $AB, BC, CD$ and $DA$ of a quadrilateral are $x + 2y = 3, x = 1, x - 3y = 4$ and $5x + y + 12 = 0$ respectively. The angle between diagonals $AC$ and $BD$ is ......$^o$

Let the line $x+y=1$ meet the axes of $x$ and $y$ at $A$ and $B$,respectively. $A$ right-angled triangle $AMN$ is inscribed in the triangle $OAB$,where $O$ is the origin and the points $M$ and $N$ lie on the lines $OB$ and $AB$,respectively. If the area of the triangle $AMN$ is $\frac{4}{9}$ of the area of the triangle $OAB$ and $AN : NB = \lambda : 1$,then the sum of all possible values of $\lambda$ is:

Two sides of a triangle have lengths $a \text{ cm}$ and $b \text{ cm}$. If the triangle is to have the maximum area,then the length of the median from the vertex containing the sides $a$ and $b$ is

In a rectangle $ABCD$,points $X$ and $Y$ are the mid-points of $AD$ and $DC$,respectively. Lines $BX$ and $CD$ when extended intersect at $E$,lines $BY$ and $AD$ when extended intersect at $F$. If the area of $ABCD$ is $60$,then the area of $\triangle BEF$ is