Total: 1239

#### The development of television sets

Television, invented in the early 20th century, became one of the basic forms of entertainment.

#### German soldier (World War I)

German sordiers in the First World War were well trained and used modern weapons.

#### British soldier (World War I)

During World War I, Britain was part of the military alliance called the ´Triple Entente´.

#### Surface area of spheres (demonstration)

The surface of a sphere consists of the set of points which are all at the same distance from a given point in space.

#### Macedonian phalangite (4th century BC)

Soldiers of the ancient Macedonian Kingdom were dreaded warriors.

#### Market town (Kingdom of Hungary)

Market towns became the most common type of towns in the Kingdom of Hungary by the Late Middle Ages.

#### Volume of spheres (Cavalieri´s principle)

Calculating the volume of a sphere is possible using an appropriate cylinder and cone.

#### Nitrogen (N₂) (intermediate)

A colorless, odorless, non-reactive gas, it constitutes 78.1% of Earth´s atmosphere.

#### Arab Caliph (7th century)

Caliphs, considered successors of the Prophet Muhammad, were the most important religious leaders of Islam.

#### Persian monarch (5th century BC)

Ancient Persian monarchs were famous for the size of their empire and their wealth.

#### American soldier (World War II)

American soldiers fought in almost all major theaters of World War II.

#### Four color theorem

Color a map with the fewest number of colors possible, so that no two adjacent regions have the same color.

#### Common blackbird

This animation demonstrates birds' bones and eggs through the example of the common blackbird.

#### Coenzyme A

An acyl-carrier coenzyme taking part in both anabolic and catabolic processes.

#### Gold mining (19th century)

The California Gold Rush started in 1848, near San Francisco.

#### Carbonate ion (CO₃²⁻)

A compound ion produced from carbonic acid by releasing protons.

#### Egyptian Pharaoh and his wife (2nd millennium B.C.)

Egyptian Pharaohs were respected as gods, they were lords of life and death.

#### The castle of Eger (16th century)

The castle of Eger got its final shape and became an important component in the new chain of border forts in the 16th century.

#### Ottoman architecture in Hungary (17th century)

Remnants of Ottoman architecture in Hungary include the Gazi Kasim Pasha Mosque in Pécs and the Minaret of Eger.

#### Coloring a cube

Coloring the vertices, edges and faces of a given cube according to the criteria specified in the exercise.