A chord is any line that touches two ends on a circle. Line segment AC is a chord.
A tangent is a line that only touches one point on the circle. The purple line on top of the circle is a tangent line.
A radius is a line from the center to any point on the circle. The red line is a radius.
A secant is like a chord, except it is a line and keeps going. The cyan (sky blue) line is a secant line.
A point of tangency is the point that the tangent line touches. The yellow point on the purple line is the point of tangency.
A diameter is a straight line that crosses the center and two points on the circle. You can say it’s two radii put together. Line segment BD (green) is a diameter.
<span>Complementary angles sum up to 90 degrees and supplementary angles sum up to 180 (I remember that because they are alphabetical).
90 - 71.4 = 18.6
180 - 71.4 = 108.6
Therefore, D. is the answer.</span>
