Answer:
∠ B = 48° , a ≈ 18.0 , c ≈ 26.9
Explanation:
∠ B = 180° - ( 90 + 42)° = 180° - 132° = 48°
using the tangent ratio in the right triangle
tan42° =
=
( multiply both sides by 20 )
20 × tan42° = a , then
a ≈ 18.0 ( to the nearest tenth )
using the cosine ratio in the right triangle
cos42° =
( multiply both sides by c )
c × cos42° = 20 ( divide both sides by cos42° )
c =
≈ 26.9 ( to the nearest tenth )