Circles Flashcards
7 cards from real Bluebook SAT Test practice questions. Tap to flip, then mark Knew It or Still Learning — missed cards come back until you master them.
Read the first 7 Circles flashcards as text
What is the center of the circle x² + y² − 10x + 4y + 20 = 0?
Answer: (5, −2)
Complete the square: (x−5)²+(y+2)² = 25+4−20 = 9; center (5,−2).
A central angle of π/6 radians corresponds to how many degrees?
Answer: 30°
(π/6)(180°/π) = 180°/6 = 30°.
A circle has diameter 14. What is its area?
Answer: 49π
r = 14/2 = 7; area = π(7)² = 49π.
An arc subtends a central angle of 5π/6 radians in a circle of radius 6. What is the arc length?
Answer: 5π
s = rθ = 6·(5π/6) = 5π.
Two inscribed angles in the same circle intercept the same arc. What is the relationship between the two angles?
Answer: They are equal
Inscribed angles that intercept the same arc are equal (both equal half the arc measure).
A circle has area 64π. How long is an arc that subtends a central angle of 45°?
Answer: 2π
r² = 64 → r = 8; arc = (45/360)(2π·8) = (1/8)(16π) = 2π.
The circle (x + 4)² + (y − 1)² = 36 has been graphed. Which point lies on the circle?
Answer: (−4, 7)
For (−4, 7): (−4+4)² + (7−1)² = 0 + 36 = 36 ✓.
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