cos A = (b^2 + c^2 − a^2) / 2bccos A = (10.4)^2 + (29.2)^2 − (22.2)^2) / (2 x 10.4 x 29.2)cos A = (108.16 + 852.64 − 492.84) / 607.36cos A = 0.77 m<A = cos−1(0.77)
m<A = 39.6
from here....you're already known the answer is C.
because only m<A = 39.6
but if you want to make sure you get it right, so you'll calculate another angle...
cos B = (a^2 + c^2 − b^2) / 2accos B = (22.2)^2 + (29.2)^2 − (10.4)^2) / (2 x 22.2 x 29.2)cos B = (492.84 + 852.64 − 108.16) / 1296.48cos B = 0.9544 m<B = cos−1(0.9544)
m<B = 17.4
So now you know for sure answer is C.
Hope it helps