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need help with example #4 Find all missing angles and sides.

Need Help With Example 4 Find All Missing Angles And Sides class=

Sagot :

We will use the law of sines and law of cosines shown below

[tex]\begin{gathered} c=\sqrt{a^2+b^2-2ab\cos C}\rightarrow\text{ law of cosines} \\ and \\ \frac{sinA}{a}=\frac{sinB}{b}=\frac{sinC}{c}\rightarrow\text{ law of sines} \end{gathered}[/tex]

Therefore, in our case, finding side c.,

[tex]\begin{gathered} a=28,b=13,C=49\degree \\ \Rightarrow c=\sqrt{784+169-2*28*13cos(49\degree)} \\ \Rightarrow c\approx21.8 \end{gathered}[/tex]

Thus, side c is approximately 21.8km.

Finding the missing angles using the law of sines,

[tex]\begin{gathered} A=\cos^{-1}(\frac{c^2+b^2-a^2}{2bc}) \\ \Rightarrow A=\cos^{-1}(\frac{21.8^2+13^2-28^2}{2*13*21.8}) \\ \Rightarrow A\approx104.3 \\ \end{gathered}[/tex]

Similarly, in the case of angle B,

[tex]sinB=\frac{13}{21.8}sin(49\degree)\approx26.7\degree[/tex]

Therefore, the answers are

c=21.8km,