Answer:
A = 51.3°, B = 90°, C = 38.7°
Explanation:
The given lengths satisfy the Pythagorean theorem:
(√41)² = 4² +5² ⇒ 41 = 16 +25
so we know the triangle is a right triangle. The right angle is opposite the longest side, so is angle B, opposite side AC.
The remaining angles can be found using trig functions. For example, we know ...
tan(A) = BC/AB = 5/4
A = arctan(5/4) ≈ 51.3°
Then the other acute angle is ...
C = 90° -51.3° = 38.7°
Angles A, B, C are ...
(A, B, C) = (51.3°, 90°, 38.7°)