How can we calculate the distance from a point to a plane in normed spaces ? where we are not inner product, for example:
Calculate the distance in $(C[0,1],||\cdot||)$ endowed with the supremum norm $$||f||=\sup_{t\in[0,1]}|f(t)|$$ from the function $f(t)=t^2$ to the linear hull of the functions $g(t)=t$ and $h(t)=\sin(t)$
Any hints would be appreciated.