Hello, im new to the forum and this is my debut thread/problem. I am currently a student enrolling in mechanical engineering at the University of Ljubljana, Slovenia. Anyways we had an exam a few days ago and it was suprising to me that only 2 people managed to get above 50% out of 100 students. The differential equation that gave me problems was this:

f(x)=ln(tg(2x))

Prove that: f "(x)+4ctg(4x)*f '(x)=0

*=product

ln=natural logarithm

tg=tangent

ctg=cotangent

if you have trouble understanding my post please reply. thank you.