eqn1 := (70*sin(x2))^2+(b*cos(x1)+70*sin(x1)*cos(x2)-550)^2+(b*sin(x1)-70*cos(x1)*cos(x2))^2-507.6^2; eqn2 := (c*cos(x2)-270*sin(x2))^2+(c*sin(x1)*sin(x2)+270*sin(x1)*cos(x2))^2+(c*cos(x1)*sin(x2)+270*cos(x1)*cos(x2))^2-554.6^2;
s := solve(eqn1, eqn2, sin(x1));
Error, invalid input: too many and/or wrong type of arguments passed to solve; first unused argument is sin(x1)

你这里的eqn1和eqn2不是等式，
用eqn1 := (70*sin(x2))^2+(b*cos(x1)+70*sin(x1)*cos(x2)-550)^2+(b*sin(x1)-70*cos(x1)*cos(x2))^2-507.6^2=0试试