Solve for Unknowns of x1, x2, x3, x4

-0.301Sin(x1)-0.501Sin(x1+x2)+0.08507Cos(x4)+0.315Cos(x4)= -0.4015

0.301Cos(x1)+0.501Cos(x1+x2)-0.08507Sin(x4)-0.315Sin(x4)= -0.3015

-0.08507Cos(62.8+x4)+0.501Sin(x1+x3)-0.501Sin(x1+x2)+0.08507Cos(x4)=0

0.08507Sin(62.8+x4)-0.501Cos(x1+x3)+0.501Cos(x1+x2)-0.08507Sin(x4)=0

Any hints or help to solve this problem is greatly appreciated.

Thanks,

Kaushik