Vector algebra

Given two vectors, $\vec{a}$ and $\vec{b}$ with norms, $\left|\vec{a}\right|=a$, $\left|\vec{b}\right|=b$ and the angle $\phi$ between them,

1.Find $\left|\vec{a}+\vec{b}\right|$.
2. Find the angle $\psi$ between $\vec{a}+\vec{b}$ and $\vec{a}$.