what am i doing wrong here? i thought i understood this. Use the parametric equations of an ellipse
x=10cosθ
y=8sinθ
0≤θ≤2π
to find the area that it encloses.

did the dx/dθ and got -10sinθ.

Question

what am i doing wrong here?  i thought i understood this.  Use the parametric equations of an ellipse 
x=10cosθ 
y=8sinθ
0≤θ≤2π 
to find the area that it encloses. 

did the dx/dθ and got -10sinθ.

anonymous · Answer

so i get $$\int\limits_{0}^{2\pi}-10\sin \theta*8\sin \theta $$

$$\int\limits_{0}^{2\pi} -80\sin ^{2} \theta $$

$$-40(\theta-\frac{ \sin2\theta }{ 2})$$

plug in 2pi for theta...but webwork says it's wrong.  what did i do wrong?

ganeshie8 · Answer

looks ok to me,
did u get A = 80pi ?

anonymous · Answer

i feel stupid. i was putting in a negative area. can't have a negative area....oops.

ganeshie8 · Answer

:)