Try this, ! the measure of a vertex angle of an isosceles triangle is 120º, the length of a leg is 8cm. find the length of a diameter of the circle circumscribed about this triangle. what is the radius in centimeters?

Check the picture below.

the triangle is an isosceles, so it has twin legs, and a base bottom.

the twin sides stem from the "vertex", and we know the vertex is 120°, and since the triangle is inscribed in a circle, because the circle is "circumscribing" it, then the base side of the triangle will be the diameter of it.

if we run a perpendicular line to the base from the vertex, we'll split the vertex in two 60° angles, as you see there, giving us a 30-60-90 triangle on each side.

so, anyhow, the rest is just a matter of using the 30-60-90 rule.

that's the diameter, and as you know, the radius is just the length of the base, or half the diameter.

Just look outside and then you’ll see where the awnser is

(answer 2 )i’m very smart that’s how i know the answer.