The voltage at a circuit node is described by $v_{GS}=(10\mathrm{.}5+4\mathrm{.}5u(t-1)+0\mathrm{.}1cos2,000t)V.u(t)$ is the unit step function.

Identify $v_{gs}$ for the given expression.

Multiple Choice

$v_{gs}=4\mathrm{.}5u(t-1)+0\mathrm{.}1cos2,000t$ Volts

$v_{gs}=4\mathrm{.}5u(t-1)+0\mathrm{.}1cos4,000t$ Volts

$v_{gs}=4\mathrm{.}5u(t-1)+0\mathrm{.}1sin2,000t$ Volts