Angles. Angles operations

ANGLES

Definition: A shape, formed by two lines or rays diverging from a common point (the vertex).
Parts: vertex, legs (rays), interior, exterior.

A triangle has three vertex

TYPES OF ANGLES

Animation.

COPYING OR TRANSLATING AN ANGLE
In Geometry, "translation" simply means moving without rotating, resizing or anything eles, just moving.

STEPS:

1. Center the compass at vertex of the given angle and draw an arc intersecting both sides of it. Without changing the radius of the compass, center it at point V and draw another arc
2. Set the compass radius to the distance between the two intersection points of the first arc.
3. Now center the compass at the point where the second arc intersects ray V.
4. Mark the arc intersection point 1.
5. Join point V with point 1 so you get the equal angle.

This page shows how to copy an angle. Given an angle formed by two lines with a common vertex, this animation shows how to construct another angle from it that has the same angle measure using a compass and straightedge or ruler.

• Step-by-step instruction sheet.

ADDING UP ANGLES

The addition of two angles is another angle whose measure is the addition of the measures of those two angles.

STEPS:

1. Copy angle A using translation of an angle.
2. From this new angle copy angle B.
3. The solution is angle C.

SUBTRACTING ANGLES

The subtraction of two angles is another angle whose measure is the subtraction of the measures of those two angles.

STEPS:

1. Copy angle B (the biggest one) using translation of an angle.
2. From this new angle copy angle A.
3. The solution is angle C.

Angles

• Angle types. By Khan Academy.

Copying an angle

• Try it yourself. Copying an angle.