Le forum de XCAS

angle_radian:=0:; solve( sin(22)=14/c, c, '=' ) [enter]
=>
"Done", set[c=37.3725402758] // ok

angle_radian:=0:; solve( sin(22.)=14/c) [enter]
The xcas application ends.

solve( sin(t)=sin(2*t) )
when the variable is not specified, I think it should be used lname cmd
solve( sin(t)=sin(2*t),lname( sin(t)=sin(2*t)) )

No crash here.
solve solves with respect to x if the variable is not specified. That will not change.

in the hpprime

solve( sin(t)=sin(2*t) ) returns [] // it can generate confusion, there are no solutions
solve( θ=10*sin(θ)) returns x
in xcas returns list[-8.42320393236,-7.0681743581,-2.85234189445,-2.02979667349e-26,2.85234189445,7.0681743581,8.42320393236]
fsolve( θ=10*sin(θ), θ, [5,7.5], bisection_solver) => [7.06817433238,7.06817440689]

other CAS, look for the variable because not always the variable x is the unknown variable. I think it should be asked about "lname" the variables of the expression and if it finds a single one, solve with respect to that variable, if it finds more than one, return a message that var should be specify.