how to find out max value of a function...

a1*thetadd - a2*cos(alpha)*alphadd + a2*sin(alpha)*(alphad)^2 + a3*thetad - a4*Vm = F_1

a5*alphadd - a2*cos(alpha)*thetadd - a6*sin(alpha) = F_2

where a1-a6 are constants, theta & alpha varies in between 0-360 deg

F_1, F_2 are functions 1 & 2 resp.

thetadd = theta double dot thetad = theta dot alphadd = alpha double dot alphad = alpha dot