2. The existence of real number X makes arccosx=2 correct, because the domain of arcsinx [- 1, 1] has a range [-π/2, π/2], while the domain of arccosx [- 1, 1].

In fact, the arcsine function

The domain of y=arcsinx is artificially defined.

Limited by the definition of one-to-one correspondence between functions,

People have defined the domain [-π/2, π/2] and the domain [- 1, 1] of sine function.

Assuming that the inverse function of this part is an arcsine function,

That is, the definition domain of the arcsine function is [- 1, 1], and the value domain is [-π/2, π/2].

The advantage is simple, and the arcsine function is also a centrally symmetric figure!