Circle Angles Area
1. Problem 33: Describe the opposite angles of a quadrilateral inscribed in a circle.
In a cyclic quadrilateral (one inscribed in a circle), the sum of each pair of opposite angles is 180°. This means the opposite angles are supplementary.
Answer: C. supplementary
2. Problem 34: Given a circle centered at C with radius 6 cm and arc AB measuring 60°, find the area of the shaded sector.
The formula for the area of a sector is $$\text{Area} = \frac{\theta}{360} \times \pi r^2$$ where $\theta$ is the central angle in degrees.
Here, $\theta=60^\circ$, $r=6$ cm.
Calculate:
$$\frac{60}{360} \times \pi \times 6^2 = \frac{1}{6} \times \pi \times 36 = 6 \pi$$ cm²
Answer: A. 6 π cm²
3. Problem 35: Name the shaded region in problem 34.
The shaded region defined by two radii and the included arc is called a sector of a circle.
Answer: B. Sector of a circle
4. Problem 36: In triangle with center A and arc DSY a semicircle, given $m\angle SAD=70^\circ$, find the measure of $\angle SAY$.
Since arc DSY is a semicircle, angle $\angle SAY$ subtended by this arc at the circumference is a right angle, i.e., $90^\circ$.
Angles in triangle SAD sum to 180°:
$$m\angle SAY = 180^\circ - m\angle SAD - m\angle ADS$$
But $m\angle ADS = 90^\circ$ (angle in semicircle).
Thus:
$$m\angle SAY = 180^\circ - 70^\circ - 90^\circ = 20^\circ$$
Answer: A. 20°
5. Problem 37: Name the shaded region which is bounded by a chord and the arc.
This shape is known as a segment of a circle.
Answer: D. Segment of a circle
6. Problem 38: Arc PQ measures 60°, radius 5 cm; find the area of the shaded segment.
First find sector area:
$$\text{Sector area} = \frac{60}{360} \times \pi \times 5^2 = \frac{1}{6} \times 25\pi = \frac{25\pi}{6}$$
Next find area of triangle formed by radii and chord:
Using formula for triangle area with central angle $60^\circ$:
$$\text{Triangle area} = \frac{1}{2} r^2 \sin 60^\circ = \frac{1}{2} \times 25 \times \frac{\sqrt{3}}{2} = \frac{25\sqrt{3}}{4}$$
Area of segment = sector area - triangle area
Approximate numeric values (using $\pi \approx 3.1416$, $\sqrt{3} \approx 1.732$):
$$\text{Sector area} \approx \frac{25\times 3.1416}{6} = 13.09$$
$$\text{Triangle area} \approx \frac{25 \times 1.732}{4} = 10.825$$
Segment area:
$$13.09 - 10.825 = 2.265$$ cm²
None of the options fit this number exactly; options are quite small, so let's check if radius might have been 5 cm as in the question. If radius is 5 cm, yes, above holds.
Among options, closest is C. 0.583 cm², but calculation shows larger.
Possibly, the answer choices imply radius different from original question or meant in different units.
We trust the method and numerical estimate.
7. Problem 39: A dart board diameter 40 cm, divided into 20 sectors; find area of one sector.
Radius:
$$r= \frac{40}{2} = 20$$ cm
Area of full circle:
$$\pi r^2 = \pi \times 20^2 = 400\pi$$
Area of one sector:
$$\frac{1}{20} \times 400 \pi = 20 \pi$$ cm²
Answer: A. 20 π cm²
8. Problem 40: Pendant is a regular octagon inscribed in a circle; lines connect opposite vertices meeting at center. Find measure of each angle at center formed.
Regular octagon has 8 vertices; central angles between vertices are:
$$\frac{360^\circ}{8} = 45^\circ$$
Lines connecting opposite vertices pass through center, forming angles equal to $45^\circ$ at center.
Answer: B. 45°