In △ A B C , ∠ A and ∠ C are both bisected by lines that are drawn to the opposite side of the triangle. What is the measure of the larger angle formed by the intersection of these bisectors if the measure of ∠ A = 58 ∘ and the measure of ∠ C = 46 ∘ ?

1 answer

To find the measure of the larger angle formed by the intersection of the angle bisectors of angles \( A \) and \( C \) in triangle \( ABC \), we start with the degrees of angles provided in the problem:

  • \( \angle A = 58^\circ \)
  • \( \angle C = 46^\circ \)

First, we can find the measure of angle \( B \) using the angle sum property of triangles, which states that the sum of the angles in a triangle is \( 180^\circ \):

\[ \angle B = 180^\circ - \angle A - \angle C \]

Substituting in the known values:

\[ \angle B = 180^\circ - 58^\circ - 46^\circ \]

Calculating the subtraction:

\[ \angle B = 180^\circ - 104^\circ = 76^\circ \]

Now, we have the measures of all three angles:

  • \( \angle A = 58^\circ \)
  • \( \angle B = 76^\circ \)
  • \( \angle C = 46^\circ \)

Next, we need to determine the angles formed by the intersection of the angle bisectors of \( \angle A \) and \( \angle C \).

The angle bisector of angle \( A \) divides it into two angles of \( \frac{\angle A}{2} \):

\[ \text{Angle from bisector of } A = \frac{58^\circ}{2} = 29^\circ \]

Similarly, the angle bisector of angle \( C \) divides it into two angles of \( \frac{\angle C}{2} \):

\[ \text{Angle from bisector of } C = \frac{46^\circ}{2} = 23^\circ \]

When the angle bisectors intersect, they form two angles at the intersection point. The angle between the two angle bisectors, denoted as \( \angle D \), can be computed as follows:

\[ \angle D = \text{Angle from bisector of } A + \text{Angle from bisector of } C \]

Calculating this gives:

\[ \angle D = 29^\circ + 23^\circ = 52^\circ \]

The angle formed by the two angle bisectors with respect to the interior of the angle between them is \( 52^\circ \). However, the angles around point \( D \) sum to \( 360^\circ \), and the two other angles formed by the intersection line will be:

\[ 180^\circ - \angle D = 180^\circ - 52^\circ = 128^\circ \]

Thus, the measure of the larger angle formed by the intersection of these bisectors is:

\[ \boxed{128^\circ} \]