Question

how to find 198th derivative f(x) = 3 sinx-2cosx

Answer 1

since it is trig I would think it alternates just find if it will be odd or even.

Answer 2

y=sin y'=cos y''= -sin y'''= -cos y''''=sin so every 4 they are the same again but since 198 is not divisible by 4 you will have to do some more work. So 198/4=49.5 round to 49 then you get 49*4=196 you then see that you have to take the derivative 2 more times. So you should find the answer by taking the derivative twice.

Answer 3

Timo86m had the right idea for a second it made me forget that that trig derivatives don't cycle every 2.