The cosine rule in triangle ABC with sides a opposite to angle A, b opposite to angle B, and c opposite to angle C is
[tex]\begin{gathered} a^2=b^2+c^2-2bc\cos A \\ b^2=a^2+c^2-2ac\cos B \\ c^2=a^2+b^2-2ab\cos C \end{gathered}[/tex]
From the given figure we can see triangle ABC with
[tex]\begin{gathered} \angle C=39^{\circ} \\ a=26 \\ b=17 \end{gathered}[/tex]
Since angle C is the angle between sides a and b
Then we can use the cosine rule to find the length of the side c
The name of side c in triangle ABC is the side AB
Then we can use the cosine rule to find side AB
AB. Yes
