How do you find the angle C formed by the sides of length 2, 3, and 7?
Not such triangle exists (you can't have a triangle where one side is more that the sum of the lengths of the other two sides).
However, to demonstrate the process:
(and noting that you could get 3 different answers depending upon which side you decide angle C is opposite.)
For demonstration purposes, I will assume the sides are
with angle C opposite side
The Law of Cosines:
can be rearranged as
for the supplied values
beyond this you should be able to do the arithmetic and look up the