we can use the photo to check
replace on the equations and notice a strange data
A. a=4 b=9 c=12
[tex]\begin{gathered} \cos A=\frac{9^2+12^2-4^2}{2\times9\times12} \\ \cos A=\frac{209}{216} \\ A=0.25 \\ \end{gathered}[/tex][tex]\begin{gathered} \cos B=\frac{4^2+12^2-9^2^{}}{2\times4\times12} \\ \cos B=\frac{79}{96} \\ B=0.60 \end{gathered}[/tex][tex]\begin{gathered} C=180-0.6-0.25 \\ C=179.15 \end{gathered}[/tex]A is right
B.a=2 b=12 c=3
[tex]\begin{gathered} \cos A=\frac{12^2+3^2-2^2}{2\times12\times3} \\ \cos A=\frac{149}{72} \\ A=\cos ^{-1}(2.069) \\ A=error \end{gathered}[/tex]arccosine has no response for values greater than 1
So, B es wrong
