The measure of ADC is 200 degrees, and lines AB and BC are tangent to this circle. What is the measure of angle ECA?

m∠ECA = 10°

Step-by-step explanation:

measure of arc AC is 360 - 200 = 160

arc AC is bisected by BE so the measure of the intercepted arc of angle BEC is 80.  Then m∠BEC = 80 since it is a central angle.  The angles formed by BE intersecting AC are right angles.  So, m∠ECA = 90 - 80 = 10

It would have been a lot easier to explain this if they had labeled the point of intersection of BE and AC

step-by-step explanation:

points a and b are equidistant from the desired line, so the line you find by using them will go through point r.

using points other than a and b will give the desired line only if they are equidistant from r. if they are randomly located, the perpendicular line you create will not necessarily go through point r, hence will not be a solution to the problem.

answer: b f g .

step-by-step explanation: