Описание презентации по отдельным слайдам:
A circle is a set of points which are all a certain distance from a fixed point known as the centre. A line joining the centre of a circle to any of the points on the circle is known as a radius. The circumference of a circle is the length of the circle. The circumference of a circle = 2 × π × the radius.
The radius of a circle is the distance from the center of the circle to the outside edge.
The diameter of a circle is longest distance across a circle. (The diameter cuts through the center of the circle. This is what makes it the longest distance.)
The circumference of a circle is the perimeter -- the distance around the outer edge. Circumference = where r = the radius of the circle and pi = 3.141592... The area of a circle Area = where r = the radius of the circle and pi = 3.141592...:
A chord of a circle is a line segment that connects one point on the edge of the circle with another point on the circle. (The diameter is a chord -- it's just the longest chord!)
An arc of a circle is a segment of the circumference of the circle.
Arc length of a circle in radians: Arc Length = Arc length of a circle in degrees: Arc Length =
A sector of a circle is a pie shaped portion of the area of the circle. Technically, the piece of pie is between two segments coming out of the center of the circle.
Sector area of a circle in radians: Sector Area = Sector area of a circle in degrees: Sector Area =
The red line in the diagram is called a chord. It divides the circle into a major segment and a minor segment.
Rules 1) When a chord subtends (makes) an angle at the circumference, the angle subtended at the centre (from the same chord) is twice as big:
2) A diameter subtends a right–angle at the circumference: 3) Angles subtended onto the circumference in each segment are equal. Angles in opposite segments add up to 180: 4) Tangents drawn from two outside points create two congruent right–angle triangles:
5) Angle between a chord and a tangent is equal to the angle subtended at the circumference in the opposite segment: