# Line, Angle, Circle

**Line: **

A line has no beginning point or ending point. You could be imagine it continuing indefinitely in both directions. We can illustrate that by little arrows on both ends.

We can name a line using two points on it. This is line EF. Or, we can name a line using a lowercase letter: this is line *s*.

**Angles:**

** **Two lines that make an angle are called rays. A ray starts out at a point and continues off to infinity. Angles are measured in degrees, each degree is 1/360 or a round trip (circle).

**1. Acute Angle: **Angle greater than 0 degree and less than 90 degree are called acute angle.

**2. Right Angle: **Angle that is exactly 90 degrees is called right angle.

**3. Abtuse Angle: **Angle that is greater 90 degrees and less than 180 degree are called obtuse angle.

**4. Straight Angle:** Angle that is exactly 180 degree

**5. Reflex Angle:** An angle that is greater than 180.

**6. Full Rotation: **It is exactly 360 degree.

**Circle:**

A line from the center of a circle to the circumference of the circle is called circle.

**Raddi: **A diameter is equal to two radii.

**Chord:** A line connecting any two points on a circle is called chord.

**Diameter: **The longest chord in a circle is the diameter. or a line going from one side of the circle to other and through the midpoint is called the diameter.

Diameter = 2 × Radius

**Circumference:** It is the distance once around the circle.

Circumference = **π** × Diameter or

Circumference = 2 × **π** × Radius

The area of a circle is **π** given by

A = **π** r^{2}

The area of a triangle is found by taking 1/2 of the product of the base and height (1/2bh).