Silly question. I have a right triangle with adjacent leg $A = 81.67$ and an opposite leg $B = -1225.53$. So hypotenuse $C$ will be $\sqrt{(A^2 + B^2)} = 1228.25$.
$\arccos(A / C) = 1.50$ and $\arcsin(B / C) = 3.07$. Why are they not the same, what is the reason of difference? ( I have used python for calculations)
P.S. Negative size means that leg goes from origin to the negative X direction
You did your computation wrong; the arcsin of $1225.53/1228.25$ is approximately $1.504$ radians.
The arcsin will never produce a value outside the range $-\pi/2 \le u \le \pi/2$, which is approximately $-1.57 \le u \le 1.57$.
(The original question had a negative-sign before the $1225.53$; in that case, the arcsin is $-1.504$ radians, again, not the same as $3.07$.)