# Deriving formula to calculate theta for artillery

I play an online shooter game with artillery that players can use. As best I can tell, the shell exits the artillery at 400m/s, I don't know if that's correct because units aren't listed in the code but it sounds logical. I know the distance to target as well, I only need to know what angle to aim the barrel to hit to target. Here's the formula I've derived as it looks in excel with A1 being the cell with the target range:
=(DEGREES(ASIN((9.81*A1)/(400^2))))/2
and in an equation, r as range to target:
(sin-1((9.81R)/(4002))/2=$$\Theta$$

The problem is that if I plug a range like 650m into it the output in excel is 1.14201, an impossible number but I know that the artillery can hit ranges over 700m. Does this imply that the 400m/s V0 I have is wrong?

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