How to find the equation of the tangent line at (pi,0) for this equation

Question

anonymous · Answer

$$\frac{ 3x^2+ysinx-3x^2\sin5y }{ 2y+5x^3\cos5y-2y }$$

anonymous · Answer

thats the derivative I got. I got 0 as the slope

phi · Answer

if that is the derivative,  the y's  and sin(y)  are all 0  and cos(y)=1
you get
3x^2/5x^3  = 3/(5x)  =  3/(5 pi)

anonymous · Answer

ok, I'm having a little problem with something, when I have something like 3x^2 sin 5x, would I do the sin 5x first then the 3x^2 or would I do it all together

phi · Answer

exactly what is the question ?

anonymous · Answer

$$3x^2\sin5x$$

anonymous · Answer

if I have something like that

phi · Answer

that is an expression.... what do you want to do with it ?

anonymous · Answer

lets say I want to know what y is when x is equal to 3, would I do the sin5x first then multiply by the 3x^2 or will I do it all together

phi · Answer

are you saying
$$ y = 3 x^2 \sin 5x $$
now evaluate at x = $ \pi$ ?

anonymous · Answer

yes, bu would I just put it all into my cal or would I do 5 multiplied by pi, then take the sin of that then multiply by 3x^2

phi · Answer

as you know,  you can change the order of multiplication
so you will get the same answer  if you did 

sin 5x  * 3  *x^2   or    3* sin 5x  * x^2  or 3*x^2  * sin 5x

anonymous · Answer

so It doesn't matter what order I do them in

phi · Answer

no,  but if x is pi ,  sin(5 pi) = 0   so you don't have to do any more work... the product will be 0

anonymous · Answer

ok thx

phi · Answer

Out of curiosity,  what is the original equation that you took the derivative of ?