If we solve the integral ∫(a, a/2) f(x)dx.

∫(a, a/2) f(x)dx, let x=a-t, then dx= -dt.

∫(a，a/2) f(x)dx = ∫(0，a/2)f(a-t)-dt = ∫(a/2，0)f(a-t)dt

In this way, we can transform an integral interval into an integral interval.

The integral interval of this problem is (π, π/2) and (π/2,0), so when we want to add and subtract, we need to convert these two integrals into an integral interval and change the problem to (π/2,0).

Of course, all of them can be changed to (π, π/2).

You try to look at it.

Newman hero 2015 65438+1October 28th 13:24:44

I hope it will be helpful to you and I hope it will be adopted.