+129847
4. When two chords intersect each other inside a circle, the products of their segments are equal.
So....
7 * 4 = 5 * z divide both sides by 5
[7 * 4 ] / 5 = z
28 / 5 = z = 5 + 3/5 = 5.6
5. We can find the radius as follows :
6 / sin 120 = radius / sin 30
6 / [ √3 / 2] = radius / [ 1 / 2 ]
6 / √3 = radius ≈ 3.46
And the diameter is twice this ≈ 6.92 ≈ 6.9
