Circle Terms And Angles
1. The set of all points in the plane that are the same distance away from a specific point, called the center, is a **circle**.
2. The distance from the center of the circle to its outer rim is the **radius**.
3. A line segment whose endpoints are on a circle is a **chord**.
4. The longest chord of a circle is the **diameter**.
5. A portion of a circle is an **arc**.
6. A line that touches the circle at exactly one point is a **tangent**.
7. A line that touches the circle at exactly two points is a **secant**.
8. An arc that measures 180° is a **semicircle**.
9. An arc that measures greater than 180° is a **major arc**.
10. An arc that measures less than 180° is a **minor arc**.
II. Without the figure, typical identifications are:
11. HF - likely a chord or segment
12. AF - likely a radius or chord
13. DG - likely a chord
14. BD - likely a chord
15. DB - same as BD, chord
16. JB - likely chord or secant
17. Point A - center or point on circle
18. Point H - point on circle or tangent point
19. HDF - likely an angle or arc
20. oA - center of circle (often denoted as O or oA)
III.
21-22. Given angle at F inside triangle FGE with inscribed circle, opposite arc measures 265°.
Step 1. The angle at F is half the measure of the intercepted arc: $$x = \frac{265^\circ}{2} = 132.5^\circ$$
Answer: $$\boxed{132.5^\circ}$$
23-24. Angles at R = 53° and L = 51°, angle at T is x.
Step 1. By circle theorems, angles subtended by the same arc relate.
Step 2. Use angle sum or inscribed angle properties (more specific figure needed).
Assuming angle at T subtends arc between R and L,
$$x = 180^\circ - (53^\circ + 51^\circ) = 76^\circ$$
Answer: $$\boxed{76^\circ}$$
25-26. For angle at E marked x,
Given arcs measure 190° and 50°.
Step 1. The measure of angle at E is half the difference of the intercepted arcs:
$$x = \frac{190^\circ - 50^\circ}{2} = \frac{140^\circ}{2} = 70^\circ$$
Answer: $$\boxed{70^\circ}$$
27-28. Angle at O marked x, arc marked 105°.
Step 1. Angle at center intercepts the arc directly:
$$x = 105^\circ$$
Answer: $$\boxed{105^\circ}$$
29-30. Angles at A is 55°, angle at O is $2x+3$.
Step 1. Assuming angle at O is central angle, angle at A is inscribed angle intercepting the same arc.
Step 2. The central angle is twice the inscribed angle:
$$2x + 3 = 2 \times 55 = 110$$
Step 3. Solve for x:
$$2x + 3 = 110$$
$$2x = 107$$
$$x = \frac{107}{2} = 53.5$$
Answer: $$\boxed{53.5}$$