Laplace transform of $$\cos \left( {\omega t} \right)$$ is

At least one eigenvalue of a singular matrix is

The surface integral $$\,\,\int {\int\limits_s {{1 \over \pi }} } \left( {9xi - 3yj} \right).n\,dS\,\,$$ over the sphere given by $${x^2} + {y^2} + {z^2} = 9\,\,$$ is __________.

At $$x=0,$$ the function $$f\left( x \right) = \left| x \right|$$ has