A certain radioactive isotope decays at a rate of 85% hourly. Determine the half-life of this isotope to the nearest minute. Use the formula A = lekt where A is the amount at time t, I is the initial amount, and k is the decay constant unique to the substance. a. 256 min
b. 14 min
c. 22 min
d. 18 min
e. 35 min

answer: the figure is attached herewith.

step-by-step explanation:   we are given to sketch a unit circle and label the terminal points corresponding to

in the attached figure, we have drawn a unit circle, with centre at o(0,0) and radius 1 unit. we have labelled the points a, b, c, d and e corresponding to the angles below

∠aox = 60°,

∠box = 120°,

∠cox = 180°,

∠dox = 240°,

∠eox = 300°.

and the coordinates are a(0.5,1), b(-0.5,1), c(-1,0), d(-0.5,-1) and e(0.5,-1).

thus, the answer is complete.

c.

explanation: