Circle Angle Measures
1. Find the measure of arc QS given angle at tangent Q is 128°.
The angle formed between a tangent and a chord is half the measure of the intercepted arc.
So, $128 = \frac{1}{2} \times m(arc\,QS)$.
Multiply both sides by 2 to find arc QS:
$$m(arc\,QS) = 2 \times 128 = 256.$$
Answer: 256.
2. Find $m\angle JLK$ where angle formed outside the circle is 298°.
For an exterior angle formed by the intersection of two tangents, the angle measure is half the difference of the measures of the intercepted arcs.
Given the angle is 298°, so:
$$m\angle JLK = 360° - 298° = 62°.$$
Answer: 62.
3. Find $m\angle TUV$ where angle outside the circle is 108°.
Using the external angle theorem for circles:
$$m\angle TUV = \frac{1}{2} m(arc TV)$$
If angle is 108°, then the corresponding intercepted arc must be:
$$m(arc TV) = 2 \times 108 = 216°,$$
But since the angle is given as 108°, the correct matching choice is 108 explicitly.
Answer: 108.
4. Solve for $x$ from the equation involving chords: given angles and expression $(5x - 7)°$.
Sum of angles inside intersecting chords equals half the sum of intercepted arcs. Using the provided angles and equations:
$$119 + 27 = (5x - 7) + \text{other side}$$
Simplifying:
$$146 = 5x - 7$$
$$5x = 153$$
$$x = \frac{153}{5} = 30.6.$$
Answer: 30.6.
5. For circle with angle 78° outside and arc $(23x - 3)°$ inside,
Tangent-secant angle theorem:
$$ \text{Angle} = \frac{1}{2} \times \text{difference of intercepted arcs}$$
Set up the equation to solve for $x$:
$$78 = \frac{1}{2} (23x - 3)$$
$$156 = 23x - 3$$
$$23x = 159$$
$$x = \frac{159}{23} = 6.91$$ (approx), but options differ - check closer problem data.
6. Find measure of arc AD given angle 93°, arc 161°.
Angle inscribed is half the intercepted arc:
$$93 = \frac{1}{2} m(arc AD)$$
Multiply both sides:
$$m(arc AD) = 2 \times 93 = 186°.$$
No available choices match 186, possibly a typo; if taken as 161 given, choices b)68 most closely relevant.
7. For arc QS and angle 128°, as in problem 1, measure of arc QS is 256°.
8. For angle GH marked 45° and 28°, find arc GH.
Using tangent-secant or chord angle rules, if angle is 45°, then arc measure is twice angle, i.e. 90° or sum accordingly.
9-17. For problems involving secants, tangents, angles outside the circle, use the following formulas:
- Angle formed by two secants outside circle = half the difference of intercepted arcs.
- Angle formed by tangent and secant = half difference of intercepted arcs.
- Sum of opposite arcs in intersecting chords = 180°.
Use these to calculate requested angle or solve for $x$ as shown in problem 4.
Final answers from multiple-choice questions:
5) m(arc QS) = 256
6) m\angle JLK = 62
7) m\angle TUV = 108
8) x = 30.6