why 360 degrees?
See also the
Dr. Math FAQ:
segments of circles
Browse High School Conic Sections, Circles
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Selected answers to common questions:
Find the center of a circle.
Is a circle a polygon?
Volume of a tank.
Why is a circle 360 degrees?
- Slope of Tangent to an Ellipse [09/21/2001]
If I know a point on an ellipse, how do I find the angle of the ellipse
at that point?
- Solve for Radius [09/09/1997]
Given a circle through three points, what is the equation for the
intersection of the perpendicular bisectors?
- Square Inscribed in a Circle [09/28/1997]
What percent of the circle is contained within the square?
- Square Peg, Round Peg [08/22/1997]
Which fits better, a square peg in a round hole, or a round peg in a
- Squares and Circles: How Many Intersections? [02/27/2002]
What is the largest possible number of times a square can intersect a
circle when the square is placed on top?
- Straight Lines and Conic Sections [10/14/2008]
Is a pair of intersecting straight lines a conic section? If so, what
is its eccentricity value?
- Strange Points of Locus [6/6/1996]
Given two fixed points, A and B, on a plane, if P is a moving point such
that PA and PB are perpendicular and the locus of P is a circle, should
we exclude points A and B?
- Symmetry Lines [03/30/2000]
How many symmetry lines are in a circle?
- Tangent Circle Construction [12/02/1996]
Given a circle with two points inside it, construct another circle that
passes through the given points and is tangent to the given circle.
- Tangent Common to Two Ellipses [10/24/2002]
I have two general ellipses in space and I want to find the equation
of the tangent common to these ellipses.
- Tangent Line and Circles [04/05/1999]
Two circles of different radius are tangent to each other. A line is
drawn tangent to both circles. How long is the segment between the two
points of tangency of the line and the circles?
- Tangents to Circles [06/25/1999]
How can I prove that a line L is tangent to Circle C if and only if L is
perpendicular to ZA, where Z is the center C and A is a point on C?
- Tangent to Parabola [10/21/1996]
What is the slope of the lines tangent to the parabola y = x^2 that pass
through the point (2,1)?
- Theorem of the Broken Chord [12/14/2001]
Prove the theorem of the broken chord (if AB and BC make up a broken
chord in a circle, where BC is greater than AB, and if M is the midpoint
of arc ABC, the foot F of the perpendicular from M on BC is the midpoint
of the broken chord).
- Three Intersecting Circles [07/14/1999]
Two circles (X^2+Y^2+4X-4Y-8 = 0 and X^2+Y^2-X-Y-2 = 0) intersect at
points P and Q. Another circle (3X^2+3Y^2-13X+KY+L = 0) passes through P,
Q, and A (3,1). What is L?
- Three Ways to Find the Vertex of a Parabola [02/19/2007]
For H(x) = -x2 - 8x - 15, what are the coordinates of the vertex, what
is the equation of the axis of symmetry, and what is the greatest
value of the function?
- Traceable Mathematical Curves [10/27/1997]
Is there any way to tell just by looking if a curve is traceable or not?
Is there some property of a curve that will tell you this? Do curves have
- Tracing an Ellipse [08/17/1997]
How do you form an ellipse using 3 points?
- Trisecting a Circle with Parallel Cuts [06/12/2002]
Can two parallel cuts divide a circle into three parts of equal size?
- Trisecting a Pizza [05/13/2002]
Without the use of a ruler, protractor or other measuring device, is
there a simple way to divide a pizza into 3 equal sized slices?
- Two Circles, Four Tangents, Collinear Midpoints [12/20/1998]
Given two circles that do not touch there are four distinct tangents
common to both circles. Prove that the midpoints of the tangents are
- Two-column Proof [5/24/1996]
Theorem: tangent segments from a point outside a circle to a circle have
- Two-Column Proof: Parallel Tangents [03/08/2002]
Prove that tangents to a circle at the endpoints of a diameter are
- Two Discs, One Rotating [7/5/1996]
Two circular discs have radii 8 cm and 28 cm. The larger disc is fixed
while the smaller disc rolls around the outside of the larger...
- Two Problems on Tangents [07/09/1998]
How can you show that the arc and the angle formed by two tangents are
supplementary? Find the radius of circle O, given the following...
- Types of Cones [01/19/1999]
Does a cone have an edge? Does it depend on what type of cone you have?
What are the different types of cones?
- Uses of Conics [05/09/1999]
What are some real life examples of conics?
- Uses of Ellipses [04/02/2003]
Where are ellipses found in real life?
- Ways to Remember the Meaning of Circumference, Radius, Diameter, and Chord [03/18/2004]
If the minute hand touched the edge of the clock, would it be most
like a diameter, radius, circumference, or chord of a circle? I have
a hard time remembering what each of those means.
- What is the Area Not Shared by the Circles? [3/3/1995]
Two circles intersect such that their centers and their points of
intersection form a square with each side equal to 3. What is the total
area of the sections of the square that are not shared by both circles?
- What is the Circumference of the Reservoir? [04/09/2003]
John and Tina start running around a round reservoir in opposite
directions, meeting for the first time after John has traveled 100
yards, and again 60 yards before Tina has completed her first lap.
- Where Will the Runners Meet? [03/29/1999]
Two runners, A and B, start 90 degrees away from each other on a circular
track and run at the same speed. If Runner B decides to cut across the
track, where will they meet?
- Which Quadrant in the Unit Circle? [11/30/1998]
Find the quadrant in which C(s) is located. Example: C(14pi/3)= C(2pi/
3). Thus, C(14pi/3) is in quadrant II.
- Who uses Ellipses? [12/3/1995]
I need to find out someone (or some occupation) that uses ellipses in
- Why 6.28 Radians? [10/07/1998]
Why is a circle divided into approximately 6.28 radians?
- Why are Manhole Covers Round? [05/09/2000]
Why are most manhole covers round? Why aren't manhole covers on the
streets squares or rectangles?
- Why Are There 2Pi Radians in a Circle? [11/24/2003]
Why are there two pi radians in a circle? I know that it has something
to do with the formula for the circumference of the circle, but I'm not
sure how it works.
- Why Is a Circle 360 Degrees? [07/01/1998]
Why is a circle defined as 360 degrees?
- Why is Area of a Circle Equal to Pi * (Radius Squared)? [07/05/2005]
I know the formula for the area of a circle is A = pi*r^2, but why
does that give the area?
- Why is Pi a Constant? [08/01/2000]
Why is the circumference of a circle divided by the diameter, or pi, the
same number for every circle?