The angle between the lines whose direction cosines are $$\left(\frac{\sqrt{3}}{4}, \frac{1}{4}, \frac{\sqrt{3}}{2}\right)$$ and $$\left(\frac{\sqrt{3}}{4}, \frac{1}{4}, \frac{-\sqrt{3}}{2}\right)$$

If a plane meets the coordinate axes at $$A, B$$ and $$C$$ in such a way that the centroid of $$\triangle A B C$$ is at the point $$(1,2,3)$$, then the equation of the plane is

The area of the quadrilateral $$A B C D$$ when $$A(0,4,1), B(2,3,-1), C(4,5,0)$$ and $$D(2,6,2)$$ is equal to

The mid points of the sides of triangle are $$(1,5,-1)(0,4,-2)$$ and $$(2,3,4)$$ then centroid of the triangle