What is the domain of $f\left(x\right)=\cos \left(x\right)$?

State the inputs and outputs of the following relation. Is it a function?

{$\left(-3,5\right),\left(0,2\right),\left(3,5\right)$}

State the inputs and outputs of the following relation. Is it a function?

{$\left(2,5\right),\left(0,2\right),\left(2,9\right)$}

Is the equation $y=-2x+10$ a function? If so, rewrite it in function notation and evaluate at $f\left(3\right)$.

Is the equation $y^2+2x=10$ a function? If so, rewrite it in function notation and evaluate at $f\left(-1\right)$.