Answer:
Step-by-step explanation:
In triangle if two sides are known and included angle is known we can use cosine formula as follows:
Say in a triangle, sides a,b are known and also included angle C
Then the third side
![c^{2} =a^{2}+b^{2} -2abCos C](https://tex.z-dn.net/?f=c%5E%7B2%7D%20%3Da%5E%7B2%7D%2Bb%5E%7B2%7D%20-2abCos%20C)
Since all values on right side are known, we can find the third side c easily.
Case II:
If alternately two sides and one angle not included is known. i.e we know a,b and either angle A or B.
then to find third side we use sine formula.
![\frac{a}{sinA}=\frac{b}{sinB} =\frac{c}{sinC}](https://tex.z-dn.net/?f=%5Cfrac%7Ba%7D%7BsinA%7D%3D%5Cfrac%7Bb%7D%7BsinB%7D%20%3D%5Cfrac%7Bc%7D%7BsinC%7D)
Using the above we can find the unknonwn side c easily.