Isaac Physics A Vertical Throw

Link https://isaacphysics.org/questions/section_7_4_question_9?board=f0add85d-5a5e-4b79-8892-cb9e73118924&stage=further_a
I've been having some issues with Part F. I've tried integrating the function v = V tan(t/T - t_f/T) as determined in previous parts, and I've applied the boundary conditions to get x= -VT ln(cos(t/T - t_f/T)) + VT ln(cos(-t_f/T)), but when i input this, the answer is incorrect. Does the answer need to be given in a specific form, or am i missing something?

Try to factor oit the term -VT (is minus VT) and combine the 2 ln term as 1 single ln term.

thank you so much, i got it

thank you so much, i got it

Can you help a little more as I tried x(t)=VTln(cos((t_f)/T)/(cos((t-t_f)/T))) a few times still it’s not working?