2019-03-20 17:05:13 +0200 asked a question Solve symbolic matrix cell I'm trying to take a cell from a matrix and solve for a variable symbolically. When I run this, I get the error: TypeError: The first argument must be a symbolic expression or a list of symbolic expressions. This is the code I am trying to execute: var('a','b','c','x','y','z') Rz = matrix([[cos(a),-sin(a),0,0],[sin(a),cos(a),0,0],[0,0,1,0],[0,0,0,1]]) Ry = matrix([[cos(b),0,sin(b),0],[0,1,0,0],[-sin(b),0,cos(b),0],[0,0,0,1]]) Rx = matrix([[1,0,0,0],[0,cos(c),-sin(c),0],[0,sin(c),cos(c),0],[0,0,0,1]]) P = matrix([[x],[y],[z],[1]]) Rzyxp = Rz * Ry * Rx * P show(Rzyxp) eqn2 = Rzyxp[2] show(eqn2) result1 = solve(eqn2==0, b) show(result1)  Any help would be appreciated