dblquad gotcha

Question Q8.2.4

What is wrong with the following attempt to calculate the area of the unit circle ($\pi$) as a double integral in polar coordinates?

In [x]: dblquad(lambda r, theta: r, 0, 1, lambda r: 0, lambda r: 2*np.pi)
Out[x]: (19.739208802178712, 2.1914924100062363e-13)


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