Given ∆ABC, m∠A=120°,b=13 cm, c=15 cm. Find the length of side a. Draw the triangle and label it. Show all work to find the missing side length. Use appropriate units.

Step-by-step explanation:

From the law of cosines we know that

The side of the triangle is .

df =

both have same length

statement #3: proof- ang is congruent to ang ecd : angles are congruent.  

step-by-step explanation:

1: the missing angles in statement #3  

a.) acb  

reason- the reason why the answer is acb is because angle ecd and angle acb are both the same size *that's what the word congruent means this is really simple.  

2: the missing word in reason #3  

c.) vertical  

reason- the reason why the answer is vertical is because the angles in that diagram on figure 2 is slanted, which is vertical, and the e and a both lay on vertical lines. along with the other's, but e and a are the 2 main points you want to focus on. and c is kind of like your starting point, because c is for both angles, not just one.  

i hope that was and understanding.