College Algebra & Trigonometry, 2018a

11.3. THE LAW OF COSINES 491
sin 38 ◦
11.8 =sin B
8
8∗ 0.61566
11.8 =sinB
0.4174 ≈ sin B
24.7 ◦ ≈ B
So with ∠A =38 ◦ and ∠B ≈ 24.7 ◦ , then:
∠C ≈ 180 ◦ − (38 ◦ +24.7 ◦ ) ≈ 180 ◦ − 62.7 ◦ ≈ 117.3 ◦
So, the angles and sides of the triangle would be:
∠A =38 ◦ a ≈ 11.8
∠B ≈ 24.7 ◦ b =8
∠C ≈ 117.3 ◦ c =17
In example 2, we’ll look at a problem in which an obtuse angle is given.
Example 2
Solve the triangle: ∠A = 110 ◦ , c =30, b =35
Round angle measures and side lengths to the nearest 10 th .
B
c =30
a
110 ◦
A b =35
C