2.1.12.6 ✓ Mathematica. Time used: 0.005 (sec). Leaf size: 12

ode=D[x[t],t]==Tan[x[t]]; 
ic={x[0]==1}; 
DSolve[{ode,ic},x[t],t,IncludeSingularSolutions->True]
 

\begin{align*} x(t)&\to \arcsin \left (e^t \sin (1)\right ) \end{align*}