Change of variables for ∫∫ sin(9x²+4y²) over ellipse 9x²+4y²=1

[pleasehelp12]

Homework Statement

Make the appropriate change of variables and evaluate $$\int\int _R\(sin(9x^2+4y^2)}\;dA$$

Homework Equations

R is bounded by the ellipse $$9x^2+4y^2=1$$

The Attempt at a Solution

I can't figure out what the substitution should be I tried u=9x^2 and v=4y^2 and that didn't work and I don't know where to go from here.

 

[Dick]

How about u=3x and v=2y? Then switch to polar coordinates in u and v.

 

[pleasehelp12]

ohhh... ok thanks. I should have seen that.