Question

Find the length of a

Question in picture attached..

Answer 1

using cosine formula a^2 = 15^2 +12^2 12(15)(12)cos(110)

Answer 2

a^2=492.13
a=22.184

Answer 3

how do you know to use cosine?

Answer 4

using the given diagram we come to know we have to apply cosine formula for this

Answer 5

yes, but how?

Answer 6

using this diagram

Answer 7

so for all problems set up this way you use cosine?