The function $$f(t)$$ satisfies the differential equation $${{{d^2}f} \over {d{t^2}}} + f = 0$$ and the auxiliary conditions, $$f\left( 0 \right) = 0,\,{{df} \over {dt}}\left( 0 \right) = 4.$$ The laplace transform of $$f(t)$$ is given by

Let $$X$$ be a normal random variable with mean $$1$$ and variance $$4.$$ The probability $$P\left\{ {X < 0} \right\}$$ is

The eigen values of a symmetric matrix are all

Choose the CORRECT set of functions, which are linearly dependent.