Using polar coordinates, evaluate the integral ∫∫Rsin(x^2+y^2)dA

where R is the region 16≤x^2+y^2≤36

1 answer

To evaluate the integral, we need to convert the integral from Cartesian coordinates to polar coordinates.

In polar coordinates, we have x = rcos(theta) and y = rsin(theta), where r is the distance from the origin to the point and theta is the angle between the positive x-axis and the line segment from the origin to the point.

The region R is defined by 16 ≤ x^2 + y^2 ≤ 36, which can be rewritten as:

16 ≤ r^2 ≤ 36.

Taking the square root of each inequality, we get:

4 ≤ r ≤ 6.

Therefore, in polar coordinates, the region R is defined by 4 ≤ r ≤ 6.

Next, we need to evaluate the integral ∫∫R sin(x^2+y^2) dA using polar coordinates.

The differential area element in polar coordinates is given by dA = r dr d(theta).

Substituting x = rcos(theta) and y = rsin(theta) into sin(x^2+y^2), we get:

sin(x^2+y^2) = sin(r^2).

Therefore, the integral becomes:

∫∫R sin(x^2+y^2) dA = ∫∫R sin(r^2) r dr d(theta).

The limits of integration for r are from 4 to 6, and the limits of integration for theta are from 0 to 2π (since we need to cover the whole region R).

Therefore, the integral becomes:

∫∫R sin(x^2+y^2) dA = ∫ from 0 to 2π ∫ from 4 to 6 sin(r^2) r dr d(theta).

Evaluating this double integral will give us the final result.