Card 1 of 8
MediumStudy card 1
Prompt
What is a circle’s circumference?
Answer
2πr, equivalently πd.
Circumference
\[C=2\pi r=\pi d\]
MathGeometry & Trigonometry
Flashcards
Circles Flashcards
Recall circle measurement, coordinate form, arcs, sectors, and tangent facts.
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Card 1 of 8. Answer hidden.
Card 2 of 8
MediumStudy card 2
Prompt
What is a circle’s area?
Answer
πr².
Circle area
\[A=\pi r^2\]
Card 3 of 8
MediumStudy card 3
Prompt
What does the standard equation of a circle reveal?
Answer
Center (h, k) and radius r.
Circle equation
\[(x-h)^2+(y-k)^2=r^2\]
Card 4 of 8
MediumStudy card 4
Prompt
What is the center-sign trap in a circle equation?
Answer
The center coordinates use the opposites of the signs shown inside the parentheses.
Card 5 of 8
MediumStudy card 5
Prompt
How do you find arc length from a central angle θ in degrees?
Answer
Multiply the circumference by θ/360.
Arc length
\[L=\frac{\theta}{360^\circ}(2\pi r)\]
Card 6 of 8
MediumStudy card 6
Prompt
How do you find sector area from a central angle θ in degrees?
Answer
Multiply the circle’s area by θ/360.
Sector area
\[A_{sector}=\frac{\theta}{360^\circ}\pi r^2\]
Card 7 of 8
HardStudy card 7
Prompt
How is an inscribed angle related to its intercepted arc?
Answer
Its measure is half the measure of the intercepted arc.
Card 8 of 8
MediumStudy card 8
Prompt
What angle does a radius make with a tangent at the point of tangency?
Answer
A right angle, 90°.
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