Question

which equation is correct regarding the measure of ∠1? o m∠1 = 1/2(a - c) o m∠1 = 1/2(a + c) o m∠1 = 1/2(b - d) o m∠1 = 1/2(b + d)

Explanation:

Step1: Recall angle - secant and secant - secant rule

The measure of an angle formed by two secants intersecting outside a circle is half the positive difference of the measures of the intercepted arcs.
Let the arcs intercepted by the secants be \(b\) and \(d\).
The formula for the measure of the angle (\(\angle1\)) formed by two secants intersecting outside the circle is \(m\angle1=\frac{1}{2}(b - d)\).

Answer:

\(m\angle1=\frac{1}{2}(b - d)\) (the third option)