If the calculation is forced, it is not a question of probability. This is an indefinite integral in calculus. Try to calculate the integral by parts. Imagine the exponential block in f(x) as v 'x.

In addition, according to the understanding of indefinite integral, that is, the physical meaning of the area on the graph in this interval, we can solve and re-associate the ω-type graph with the standard normal distribution. The area between the whole graph and the X axis is 1, so the area of the negative semi-axis of the X axis is 0.5.