The formula below gives a result of 79.935 degrees using calculator
cos A = (b² + c²) - a² / 2bc
a=25.0 in A57
b=21.5407 in B57
c=17.0 in C57

This formula below has error which I cannot fix.
I have been trying for a while with no luck.
It could be that I'm trying to approch it the same way as a calculator.
In E57
=IF(OR(A57="",B57="",C57=""),0,DEGREES(ACOS(B57^+C 57^)-A57^/2*B57*C57)))

Or in E57 =IF(COUNT(A57:C57)<3,0),0,DEGREES(ACOS(B57^+C57^)-A57^/2*B57*C57)))
My answer should be 79.935 degrees
Does someone have an answer for this puzzle?
Many thanks in advance.
Serge