Supplement: Ellipse area formula: S=π (pi) ×a×b, where a and b are the lengths of the semi-major axis and semi-minor axis of the ellipse, respectively.
2. The difference between the first kind of curve (surface) integral and the second kind of curve (surface) integral.
3. About integral symmetry
Some conclusions about zero integral: First of all, digression: Only the first kind of curve integral, the first kind of surface integral, definite integral, double integral and triple integral can make use of the symmetry of integral. Remember one sentence: Look at the given interval symmetrically, and look at the parity of the integrand function.
Surface integral of the second kind
The first kind of surface integral has so-called parity symmetry (parity zero), while the second kind of surface integral does not have parity symmetry, but is determined according to the positive and negative sides of the surface, and the properties are just the opposite: if the integral surface is symmetrical, the integrand is odd function with respect to the corresponding variable, and the integral is twice as large as the half interval; If it is an even function, the integral is equal to 0. Refer to the following analysis: