1. ## implicit help

can someone help me with this problem?

Find as a function of if .

i know it should be easy but i must be doing something stupid incorrectly because the answer i got was wrong

2. Originally Posted by purplegirl1818
can someone help me with this problem?

Find as a function of if .

i know it should be easy but i must be doing something stupid incorrectly because the answer i got was wrong
just differentiate both sides. the left side becomes $\frac {d^2x}{dt^2}$ and the right side becomes $\text{derivative of}(9x \cos x)~\frac {dx}{dt}$

Originally Posted by purplegirl1818