21. identify the secant that intersects OA.

Explanation:

A secant line cuts the circle so that part of the line is inside the circle, and the rest (or majority) of the line is outside the circle. In other words, the secant line intersects the circle at exactly two points.

This is in contrast to a tangent line that only touches the circle at exactly one point. Line L is the tangent line in this case.

Segment DC is a diameter of the circle as it goes through the center, and this segments endpoints are on the circle's edge. The segments AD and AC are radii of the circle.

Line BC

Step-by-step explanation:

step-by-step explanation:

the original amount doesn't ''re just looking for the time it takes for 1/2 of the substance to we have

(1/2) =)     take the ln   of both sides

ln (1/2)   = )   and we can write

ln(1/2) = ) lne     and lne   = 1     so we have

ln(1/2) = -.1092t     divide both sides by -.1092

t = ln(1/2)/-.1092 = about 6.347 days = about 6.3 days (rounded)