Circes Flashcards
What is a central angle?
two points A and B, lines from them to center of the circle form the central angle ∠AOB
How to find the arc using central angle?
The arc is the same as the angle.
What is a tangent of a circle?
When a line intersects a circle at one point.
What angle is formed when the radius touches the tangent?
a 90 degree angle
Two minor arcs are congruent if their corresponding chords are congruent. True or false?
True
What happens if the diameter is perpendicular to a chord?
It bisects the chord and the arc, making them equal
When are two chords congruent?
When they are equidistant from the center.
What is A central angle equal to?
It’s arc
What makes an angle inscribed?
If it’s vertex is on a circle and its sides contain chords.
when we have the measure of an inscribed angle how can we use it to find it’s intercepted arc?
The arc is two times the angle. If we have the arc the angle is half of the arc
What are two properties of an inscribed angle?
(1) if it intercepts a semi circle in the angle is 90 (2) it quadrilateral is inscribed then opposite angles are equal to 180
What is a point of tangency?
Line intersects Circle at one point.
If a line is perpendicular to the radius and its endpoint is on the circle, what do we know?
The line is tangent
If two segments from the same exterior point are tangent to a circle what do we know?
We know that they are congruent
What is a circumscribed polygon? What do we know about the lines?
When a circle is inside a polygon. They are all tangent and therefore equal.
What is a secant?
Line that intersects a circle at exactly 2 points
What are the measure of a secant’s angles related to?
Intercepted arcs.
If two secants intersect inside a circle, what formula do we use?
Measure of angle one = 1/2(mARC1 + mARC2)
If the center of a circle is (2,3), and the radius is 5, what equation do we set up?
(x-2)squared + (y-3)squared = 5 squared
Positive numbers in the equation, (x-h)squared + (x-y)squared are actually what?
Negative
When graphing a circle what is most important to find?
The center and radius.
What is an inscribed polygon?
Polygon that has all vertices inside circle
when a circle is circumscribed about the polygon, what does that mean?
the circle is around the polygon
