An official stands 2 meters from the edge of a discus circle and 3 meters from a point of tangency.Find the radius of the discus circle?

Answer 1

Use Pythagoras

3^2 = r^2 + (2 + r)^2

9 = r^2 + 4 + 4r + r^2

2r^2 + 4r = 5

Complete the Square

r^2 + 2r = 5/2

(r + 1)^2 - 1^2 = 5/2

(r + 1)^2 = 5/2 +1 = 7/2

r + 1 = +/- sqrt)7/2)

r = -1 +/-sqrt)7/2)

r = -1 +/- sqrt(3.5

r = -1 +/- 1.8708....

r = -2.8708.... (Unresolved!!!! Philosophically you cannot have a negative length).

& r = 0.8708.... The answer!!!!