5x(cos 9x-1)/sin 5x-5x
The Attempt at a Solution
answer is 243/25
The derivative of sin 5x-5x is always 0,
dunno know how to do it...
You'd use the rule if you got a 0 in the denominator after plugging in the limit of x, not if it were 0 to begin with. An equation over 0 would always be over 0 no matter how many times you differentiate it.
Edit: Actually I think you meant if you differentiate zero you get zero...
I differentiated like 5 times, I still got 0..
I notice that there is always a x*cos(9x) in the nominator...which make whole thing equal to 0..