What is m ∠dec if measure of arc dc = 150° and measure of arc ab = 90°? a. 150° b. 120° c. 240° d. 90°

B.

Step-by-step explanation:

We have been given an image of a circle. We are asked to find the measure of angle DEC.

Upon looking at our given circle, we can see that angle DEC is formed by the intersection of secants AC and BD inside the given circle.

We know that intersecting secants theorem states that angle formed by two secants inside the circle is half the sum of intercepted arcs.

Using intersecting secants theorem, we can set an equation as:

Therefore, measure of angle DEC is 120 degrees and option B is the correct choice.