Point is, you need two sides of the triangle and the angle between them.
BTW I always like to keep the solutions exact where possible, hence the square root value rather than the decimal.
I'm not sure why you reposted this question when I already answered it in your other thread: http://www.mathhelpforum.com/math-he...-triangle.html. Did you not see it?
The answer is not .
The answer is .
Notice that when you put it into the calculator you get a decimal answer. This is NOT exact, it is a decimal approximation to .
You have done the right thing but have gotten the decimal answer rather than the exact answer.