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#### Festival to scare away winter

In many cultures the traditional ritual of scaring away the winter is still practised, although today the performance is mainly just tourist attraction.

#### The rock cycle

Due to the effect of both exogenic and endogenic forces, rocks constantly change. This is called the rock cycle.

#### Long-tailed mayfly

Mayflies or shadflies are insects whose larval stage usually lasts 1-3 years, which they spend in freshwater.

#### Reflecting a line segment across an axis

Axis t and line segment AB are given on a plane. Let’s plot the mirror image of line segment AB across t.

#### Sarcophagus

The recording shows a more than 2000-year-old gilded sarcophagus. You can see the names of the deceased and his protecting gods on the coffin.

#### 35mm cinema projector

Watch this video to learn how a cinema projector works and how a film appears on the screen.

#### Reflecting a circle across an axis

Axis t and a circle with centre O and radius r are given on a particular plane. Let’s plot the mirror image of the circle.

#### How airbags work

A compound called sodium azide is responsible for the operation of airbags.

#### The hot ice experiment

The words hot and ice together? There must be a trick somewhere. Let’s have a look.

#### Plotting a perpendicular to a line at a given point P on the line

Both line e and point P, which is situated on it, are given. Let’s plot line g to include point P on line e so that it is perpendicular to line e.

#### Plotting a perpendicular on a line from a point P that is not on the line

Both line e and point P, which is not situated on line e, are given. Let’s plot line g such that it passes through point P and is perpendicular to line e.

#### Archimedes' seesaw

In this experiment, we use buoyancy to study the balance of two glasses of water.

#### Plotting parallel lines – Solution I

Let’s plot line g such that it is parallel to line e and passes through point P.

#### Plotting parallel lines – Solution II

Let’s construct a rhombus such that one of its sides lies on line e and point P is one of the vertices on the opposite side.

#### Archimedes’ principle with gases

Is there a difference between the weight of a plastic bottle filled with air and the weight of a crushed one?

#### Development of the carnation flower

The carnation is considered as the national flower of Spain. Let's see how the flower develops.

#### Constructing the perpendicular bisector of a line segment

Let’s construct the perpendicular bisector of a 6-cm-long line segment.

#### Plotting an angle bisector

In this video, we plot the angle bisector of a given alpha angle.

#### The focus of a jar

Studying the focal point of a jar filled with water.

#### How to copy an angle

Let’s copy a given alpha convex angle onto ray f with starting point F.