Check your post...are you sure about the 120? Doesn't that look impossible to you?!
Looks more as if the angle is 120 degrees, and you're to find arc's length...
1. Have a look here: Inscribed angle - Wikipedia, the free encyclopedia
2. As far as I understand your question you have to evaluate the length of the radius first. Use the indicated right triangle. Keep in mind that
3. To determine the length of C use proportions:
Divide triangle into two right angled triangles
Let r=radius. So sin60=3/r root3/2=3/r r=6/root3=6root3/3=2root3
area sector 1/3pir^2 =1/3pi.12=4p
Let height of triangle =h Then tan60=3/h h=3/tan60=root3
Area of triangle=1/2.6.root3=3root3
Segment=sector-triangl
That's not what's asked for, Biff.
The problem, PROPERLY worded:
chord AB = 6 cm
angle AOB = 120 degrees
calculate length of arc ACB
...to which Earboth shows the steps to solution.
An arc SUPPORTS a central angle; is NOT equal to a number of degrees:
it has its own length, which is part of the circle's circumference.