nonlinear first order diff. eq. system

dx/dt = a*sin(y[t]) + b,

dy/dt = a*cos(y[t])/x[t] - b*tan(y[t])/x[t],

dz/dt = tan(y[t])

i.c.: x(0)=300, y(0)=1,2741, z(0)=0

z vs t ??

(a=121.078, b=0.001)