∆ABC with m∠A = 38° and AB = 6.3 and BC = 4.2
Using law of sines:
∠C is an acute (QI) angle and ∠AC'B is an
obtuse (QII) angle. They have the same sine and are
supplementary.
Using the inverse sine feature of our calculator,
∠C = 67.44208077°
so ∠AC'B = 180°-67.44208077° = 112.5579192°
To find side AC and AC', we use the law of cosines:
Swap sides:
Rearrange terms and a factor with 0 on the right:
Use the quadratic formula
Using the + gives us AC = 6.575659859
Using the - gives us AC' = 3.353275637
We can find ∠ABC and ∠ABC' by adding the
two angles we now know and subtracting from 180°.
You can finish that part.
Edwin