showtime:true$ loadprint:false$ eqn1:a*cos(p2)=s+b*cos(p3); eqn2:a*sin(p2)=e+b*sin(p3); /* declare p2, p3 and s to be time-dependent. */ depends([p2,p3,s],t); /* [1] from equations 1 and 2, eliminate p3: */ eqn3:expand((eqn1-s)^2+(eqn2-e)^2); eqn3:trigsimp(eqn3); /* [2] using the results of step 1, solve for s in terms of a,b,e,p2: */ s_solution:solve(eqn3,s); /* note that this differs from the result given. [3] take the derivative of eqn2 wrt t: */ eqn3:diff(eqn2,t); /* [4] solve for p3-dot in terms of a, b, p2, p2-dot,p3. */ p3_dot:solve(%,diff(p3,t)); /* [5] take the derivative of eqn2 wrt t: */ eqn5:diff(eqn1,t); /* [6] solve for s-dot in terms of a, b, p2, p2-dot,p3. */ solve(eqn5,diff(s,t)); %,p3_dot,factor; trigreduce(%); /* [7] */ z:i*(a*cos(p2)/(b*cos(p3)))^2; diff(z,p2);