I am new to mathematica and I am having this issue in this piece of code.
x=0.1Sin[[Pi]/8t+[Pi]/4] (* this is my original function*) v=D[x,t] (* took the 1st derivative and got 0.0392699Cos[pi/4+pi/8t)
Once I got the expression for the 1st derivative, I solved for the equation and got (-6,2) as a solution. The problem starts when I take derivative of v to get an expression for acceleration. a=D[v,t] The above code gives me -6 is not valid variable error. Any kind of help would be greatly appreciated. FWIW,I am doing this in mathematica online.