derivative!! help!!::: y=2sinx-5cosx

Question

derivative!! help!!:::  y=2sinx-5cosx

anonymous · Answer

Do one term at a time.

anonymous · Answer

i know for stuff like :x^3+x^2, it's just = 3x^2+2x
but how would you do it one by one for SIN and COS??

anonymous · Answer

derivative of sin= cos
derivative of cos=-sin

anonymous · Answer

Is the first part -2cosx?

anonymous · Answer

ohh, so it's just -2cosx +5sin?

anonymous · Answer

You have the derivatives in my note above. Please note the signs.

anonymous · Answer

aaak I subtracted  should be added:  f'g + g'f
f=2
f'=0
g=sinx
g'=cos x         0*sinx + cosx * 2     but for reasons known only to my brain I wanted to subtract
 so first part is 2 cosx   no negativity

anonymous · Answer

bad kantalope! trying to do things in head

anonymous · Answer

No multiplication rule.

anonymous · Answer

no? uh oh....what rule should I be usin?

anonymous · Answer

Since they are added, you just find the derivative of each.

anonymous · Answer

right so 2sinx is two times sine x ya?   how come no multiplication rule?

Ah because it is not (2x)sinx......so should treat it like coefficient in 3x^2

anonymous · Answer

Right 2 is just a coefficient, it goes along for the ride, as they say.

anonymous · Answer

well dang it - that explains some of my test scores lol

anonymous · Answer

It takes time to sink in. You've got it now.

anonymous · Answer

this is the answer
2cosx+5sinx

anonymous · Answer

i hope my memory did not tell me wrong.:)lol