It must be a pair of methods, because the integrand is odd function and the integral interval is symmetrical about the origin, and the result is absolutely 0.

Error reason of method 2: (1) The positive-negative relationship between -π/2 and 0 to π/2, from -π/2 to 0, and from 0 to π/2 is wrong.

(2) If the integrals are to be added, it can be counted as multiplication. The sum is exactly 0.