Circles Flashcards
Радиус (ед. ч и мн. ч.)
radius, radii
Длина окружности
circumference
segment with two points on the circle
chord
chord that passes through the center
diameter
curved piece of the circle line
arc
2 types of arc measurement
- arc measure/size is in degrees
- arc length is in cm/mm and other
Касательная
tangent line
a slice of a circle
circular sector
Stretagecially most powerful measure to look for (in quantative tasks)
radius
Circular properties
- Any triangle with two sides that are radii has to be isosceles;
- If the “chord side” of such a triangle is also equal to radius, then the triangle is equilateral.
Types of angles in circles and their relation to arcs they sit on
- central angle, equal to the arc it sits on;
- inscribed angle, twice less than the arc it sits on.
Special case of an inscribed angle
Any inscribed angle that intercepts a semicircle must be a right angle.
Area of a circle formula
πr²
Circumference formula
2πr or πd
π
π ≈ 3.14
OR
π ≈ 22/7
part of a circumference
arclength
area of a sector formula
area of a sector/πr² = angle/360
or
area of a sector/r² = angle/2 if angle is in radians
arclength formula
arclength/2πr = angle/360
or
arclength/2r = angle/2 if angle is in radians
the standard form of equation of the circle
(x - h)² + (y - k)² = r², where (h,k) are the coordinates of the centre
