Answer:
Below in bold.
Explanation:
Using the Cosine Rule:
a^2 = b^2 + c^2 - 2bc cos A
10^2= 11^2 + 13^2 -2.11.13 cos A
cos A = (11^2 + 13^2 - 10^2) / (2*11*13)
= 0.66434
m < A = 48.368 degrees
= 48.37 degrees to 2 D. P's.
By the Sine Rule:
a / sin A = b / sin B
10 / sin 48.368 = 11 / sin B
sin B = 11 * sin 48.368 / 10
= 0.82217
m < B = 55.303
= 55.30 degrees to 2 D,P's
So, m < C = 180 - 48.37 - 55.30
= 76.33 degrees