the formulas (a better name is equation) are:

c^2 = a^2 + b^2 - 2*a*b*cosC

a^2 = c^2 + b^2 - 2*c*b*cosA

b^2 = a^2 + c^2 - 2*a*c*cosB

(^2 means square)


now:

you cannot use the law of sines, right? (it would be easier).... so, use the third one:

61^2 = 51^2 + c^2 - 51*2*c*cos(19)

this is: c^2 + 102cos(19)*c - 1120 = 0

using Vietta, or any other method for cuadratic ecuations you get this:

c = - ( squareroot(2061*(cos(19))^2 + 1120) - 51 cos (19) ) or
squareroot(2061*(cos(19))^2 +1120) + 51 cos(19)

aproximately:

c = 110.943 or -10.095

don't use the the negative one for obvious reasons, so...

c = 110.943

use this to get the other ones...

EDIT: oops.. 19 is the external angle... that changes it

Rock lee: Please be mindful that using the edit button is preferable to using the 'post reply' button whenever it would result in a double post. I edited your post to include your double post, and deleted the double post.-- Bobslob