Question 684448
a^2 = b^2 + c^2 - 2*b*c*cos(A)


49 = 4^2 + 5^2 - 2*4*5*cos(A)


49 = 16 + 25 - 40*cos(A)


49 = 41 - 40*cos(A)


49 - 41 = -40*cos(A)


8 = -40*cos(A)


8/(-40) = cos(A)


-1/5 = cos(A)


cos(A) = -1/5


A = arccos(-1/5)


A = 101.536959


So the angle A is roughly 101.536959 degrees.


I'll let you find angles B and C