Question

Question 3Use the Law of cosines to solve triangle ABC given that a = 15, b = 11, and c = 21.[A] A=342*, B=30.1, C=115.7"[B] A = 43.29, B = 30.1°, C = 106.7°[C] A = 23.4 B = 10.31.0=146.3|||[D] A=423*, B=310',C= 107.6*

Answer 1

Given

a=15

b=11

c=21

Find

all angles of the triangle

Step-by-step explanation

Using law of cosine to find angle A

`\begin{gathered} A=\cos^(-1)\lbrack(b^2+c^2+a^2)/(2bc)] \\ =\cos^(-1)[(11^2+21^2-15^2)/(2*11*21)] \\ =43.29 \end{gathered}`

Similarly

`\begin{gathered} \angle B=30.1 \\ \angle C=106.7 \end{gathered}`

Final Answer

option (b) is correct