However, commands in the Symbolic Math Toolbox enable you to enter formulae such as sin(2*x), x*exp(x), x^2+3*atan(x), cos(x)^2+sin(x)^2, etc, where x is a symbolic variable.
For example if you merely enter the single command sin(x) after the prompt you receive the error message A variable x must have a numerical value (or array values) before expressions involving x can then be evaluated. In all previous sections of this introduction MATLAB has been used as a powerful programmable graphics calculator.
