9. Determine how long it takes for 80% of the material to decay. lodine 131, used in nuclear medicine, initial amount 85 milligrams, half-life 8 days.

step-by-step explanation :

we know that

the measurement of the outer angle is the semi-difference of the arcs which comprises

in this problem

m< xzy is the outer angle

substitute the values

the measure of angle xoy is equal to

> by central angle

substitute the value

the answer is:

mean: 6

mad: 2.14