If a man running around a race-course notes that the sum of the distances of two flag-posts from him is always $$10 \mathrm{~m}$$ and the distance between the flag-posts is $$8 \mathrm{~m}$$, then the area of the path he encloses in square metres is
If a circle of constant radius '$$r$$' passes through the origin and meets the coordinate axes at points $$A$$ and $$B$$ respectively, then the locus of the centroid of triangle $$O A B$$, '$$O$$' being the origin, is
A ray of light is sent along the line $$x-2 y+5=0$$. Upon reaching the line $$3 x-2 y+7=0$$, the ray is reflected from it. The equation of the line containing the reflected ray, is
A unit vector perpendicular to both the vectors $$\hat{\mathbf{i}}+\hat{\mathbf{j}}$$ and $$\hat{\mathbf{j}}+\hat{\mathbf{k}}$$ is