How do you find x when 18²=10²+12²-2*10*12cos(x)

You would have to get everything to one side except for the cosine(x)

It would look somewhat like this

cosx = (18^2-100-144)/-240

Once calculated out. You find where cosx where equal that answer.

So it would be where does cosx = -1/3. Then you solve for that

only 10/60 isn't equivalent

hope this : )