Answer:
Step-by-step explanation:
The relevant relations here are ...
- the sum of arc measures in a semicircle is 180°
- the sum of angles in a triangle is 180°
<h3>Arc measures</h3>
The given arc CD is part of the semicircular arc CDA. The remaining arc, DA, is the supplement of CD:
arc DA = 180° -CD = 180° -125° = 55°
Central angle AOD has the same measure, 55°. That is one of the acute angles in right triangle AOB, so the other one is the complement of 55°.
∠ABO = 90° -∠AOB = 90° -55°
∠ABO = 35°
<h3>Triangle angles</h3>
In right triangle ABC, angle ABC is given as 55°. The other acute angle, ACB, will be the complement of this.
∠ACB = 90° -∠ABC = 90° -55°
∠ACB = 35°
In the figure, angles ABO and ACB have measures of 35°.
