Phase between two sinusoids and which one is leading
You have got these two equations: 
$$v1(t) = 4*cos(377t + 10)$$ and
$$v2(t) = 20*cos (377t+180)$$
If you substitute t=0, you will get \$v1(0) =  4*cos(10)\$ and \$v2(0) = 20*cos(180)\$. From the values you can conclude that at t =0, v2 has a value which cosine does at the end of its period and v1 has a value which cosine does at the beginning of its period.
So, we can say v2 is leading v1.