# Implicit Defferentiation

• April 7th 2010, 12:56 AM
Imaginary
Implicit Defferentiation
Hello everyone,

I got two problems that I need help with:

Find dy/dx

1- cos 3y = tan 2x

2- x cos y = sin(x+y)

Thank you so much!
• April 7th 2010, 02:54 AM
CaptainBlack
Quote:

Originally Posted by Imaginary
Hello everyone,

I got two problems that I need help with:

Find dy/dx

1- cos 3y = tan 2x

2- x cos y = sin(x+y)

Thank you so much!

What have you tried? In both cases differentiate noth sides with respect to x and then rearrange to find dy/dx

CB
• April 7th 2010, 02:59 AM
Air
Quote:

Originally Posted by Imaginary
Hello everyone,

I got two problems that I need help with:

Find dy/dx

1- cos 3y = tan 2x

2- x cos y = sin(x+y)

Thank you so much!

Differentiate both sides with respect to $x$ and then rearrange to make $\frac{\mathrm{d}y}{\mathrm{d}x}$ the subject.

1.
Alongside implicit differentiation, use chain rule when differentiating both sides.

2.
Alongside implicit differentiation, use product rule when differentiating LHS. For RHS, alongside implicit differentiation, use product rule and chain rule when differentiating.