If $P(3,2,6), Q(1,4,5)$ and $R(3,5,3)$ are the vertices of $\Delta PQR$,then $m \angle PQR$ is (in $^{\circ}$)

The circumcentre of the triangle formed by the points $A(3,4,5)$,$B(2,3,1)$,and $C(-1,6,1)$ is:

If the points $P = \hat{i} + 2 \hat{j}$,$Q = 4 \hat{i} + 6 \hat{j}$,$R = 5 \hat{i} + 7 \hat{j}$,and $S = a \hat{i} + b \hat{j}$ are the consecutive vertices of a parallelogram $PQRS$,then:

$ABCD$ is a parallelogram,$P$ is the mid-point of $AB$. If $R$ is the point of intersection of $AC$ and $DP$,then $R$ divides $AC$ internally in the ratio

If the three vertices of a parallelogram are $(-1, 0), (3, 1),$ and $(2, 2)$ respectively,find the coordinates of the fourth vertex.

The points $(5,-4,5), (-3,-3,2)$ and $(-1,-6,8)$ form ......