Hi,
I can't figure out the intermediary steps in the following calculation (example 8.11 Electric Circuits 10th Edition)

\$\alpha = 2800 Rad/Sec \quad and \quad \omega_{d} = 6800 Rad/Sec\$
The solution is given
\$i(t)=B_{1}e^{-\alpha t}cos(\omega_{d}t)+B_{2}e^{-\alpha t}sin(\omega_{d}t)\$
Since \$B_{1}=0\$ the cos part drops out and the solution becomes
\$i(t)=B_{2}e^{-\alpha t}sin(\omega_{d}t)\$
Therefore
\$\frac{d i}{dt} = 400 B_2e^{-2800t}(24cos(9600t)-7sin(9600t))\$
Herein lies my problem, how did they arrive at the "therefore" part? I can't figure the steps out, I assume the right hand side is the derivative of the solution, but when I try calculate the derivative I get:
\$\frac{d i}{dt} = B_2e^{-\alpha t}(\omega_{d} cos(\omega_{d} t)-\alpha sin(\omega_{d} t))\$
It looks a bit like above but the constants are not the same, and where did they get 400 from?