- #1

- 1,045

- 2

## Homework Statement

Differentiate:

y= u(a cos(u) + b cot(u))

## Homework Equations

No Chain Rule

## The Attempt at a Solution

I started out finding the derivative of (a cosu + b cotu)

I'm guessing that a/b is constant?

[tex]\frac{d}{du}(a cos(u) + b cot(u))=[/tex]

[tex]=(0(cosu)+a(-sinu))+(0(cosu)+b(-csc^2u))[/tex]

[tex]=(0+a(-sinu))+(0+b(-csc^2u))[/tex]

[tex]=(-asin(u)-bcsc^2(u))[/tex]

So then I used that and the product rule:

[tex]y'=1(a cos(u) + b cot(u))+u(-asin(u)-bcsc^2(u))[/tex]

[tex]y'=a cos(u) + b cot(u)-uasin(u)-ubcsc^2(u))[/tex]

Pretty sure I am making a huge mistake here, it doesn't feel right at all?

Last edited: