Diagram here: http://img172.imageshack.us/img172/1344/trig.jpg
What is the length from B to C?
What is the area of triangle?
Use the Law of Cosines to find the length of BC:
So the length of BC is about 23.13 m.
Then use Heron's formula to find the area. If you have a triangle with side lengths a, b & c, the formula is
In our case:
So the area of the triangle is about 127.28 sq. m.
in the answer given by yeongil, Heron's formula was used Heron's formula - Wikipedia, the free encyclopedia
hope this helps