It is proved that the equation x = asinx + B (a > 0, b > 0) has at least one positive root not exceeding a + B

It is proved that the equation x = asinx + B (a > 0, b > 0) has at least one positive root not exceeding a + B

Let f (x) = x-asinx-b. it is proved that f (x) has at least one positive zero which does not exceed a + B. obviously, f (x) is continuous
f(0)=-b=0
If f (a + b) = 0, then the original proposition holds;
If f (a + b) > 0, then the two end functions of F (x) in [0, a + b] have different sign values, and f (x) is continuous. According to the zero point theorem, x0 belongs to (0, a + b) such that f (x0) = 0