why do I receive syms requires Symbolic math tool box

syms M m L q d_q dd_q x d_x dd_x g b J F
eq1= (M+m)*dd_x + m*L*(dd_q*cos(q)-d_q^2*sin(q))+b*d_x-F;
eq2= (J+mL)*dd_q+m*L*dd_x*cos(q)+m*L*g*cos(q);
solu=solve(eq1,eq2,dd_x,dd_q)
solu.dd_x
solu.dd_q

Answer 1

[Stephan]

"why do I receive syms requires Symbolic math tool box?" - Simple: Because syms is part of the symbolic toolbox. If your license doesn't cover that toolbox you are not able to use it's features.

In eq2 i replaced (J+mL) through (J+m*L):

syms M m L q d_q dd_q x d_x dd_x g b J F
eq1= (M+m)*dd_x + m*L*(dd_q*cos(q)-d_q^2*sin(q))+b*d_x-F;
eq2= (J+m*L)*dd_q+m*L*dd_x*cos(q)+m*L*g*cos(q);
solu=solve(eq1,eq2,dd_x,dd_q)

solu = struct with fields:
    dd_x: (F*J + F*L*m - J*b*d_x + L^2*g*m^2*cos(q)^2 + L^2*d_q^2*m^2*sin(q) - L*b*d_x*m + J*L*d_q^2*m*sin(q))/(- L^2*m^2*cos(q)^2 + L*m^2 + M*L*m + J*m + J*M)
    dd_q: -(L*m*cos(q)*(L*m*sin(q)*d_q^2 + F + M*g - b*d_x + g*m))/(- L^2*m^2*cos(q)^2 + L*m^2 + M*L*m + J*m + J*M)

solu.dd_x

ans = 

solu.dd_q

ans = 

[Luqman Alabri]

thank you so much🌹