# NDSolve::underdet While trying to solve Differential

A = 1.06
d = 0.0208
w = 2*Pi
w0 = 5 * w
w1 = 9.987 * Pi
b1 = x[0] - A * Cos[d]
B = w0/20
b2 = (1/w1)*(x'[0] - w * A * Sin[d] + B * b1)

s = NDSolve[{x[t] == A * Cos[w*t - d] + E^(-B* t)* (b1*Cos[w1*t] + b2 *
Sin[w1 * t]), x[0] == 0, x'[0] == 0}, x, {t, 0, 10}]


The differential seems like it should work, do not understand why I am getting this error . Thanks for any help

• I do not see any differential equation...am I missing something?
– zhk
Mar 14 '19 at 18:32
• b1 and b2 are supposed to be unknown but i put in the solution that the textbook gave. Our prof wants us to solve it numerically on Mathematica instead of analytically like the text. Sorry we do not have a diff eq class offered and it is not covered in depth in our calc 3. b1 and b2 in the original equation do not have values
– jack
Mar 14 '19 at 18:45
• I cannot reproduce the issue because I obtain the error NDSolve::litarg instead. As zhk has already said, the first argument of NDSolve is not a differential equation. So, please check your input. Mar 14 '19 at 18:57
• @jack Can you share info about the text book? title, page number...or a screenhot of the particular details will also work...
– zhk
Mar 15 '19 at 2:57