Mathematics
English
Two arms, one vertex—make an angle
A catchy cardboard-crocodile song shows how two angle arms begin at one shared vertex. Children discover that an angle changes when the arms turn, while shortening an arm without turning it leaves the angle unchanged.
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Text from the recording’s subtitles.
Song lyrics
What made this cardboard crocodile click?
Lena cuts two brightly colored strips.
A round rivet joins them at one end.
Click—both strips can turn around the dot.
She moves one strip; the jaws open wide.
Both angle arms start at that same dot.
That shared starting point is the vertex.
Two arms, one vertex—make an angle.
Spread them wider; the angle grows.
Bring them closer; it gets smaller.
The arms' directions set its size.
A small paper fish fits a narrow gap.
The big fish needs the jaws open wider.
Lena spreads the arms; the angle grows.
She brings them closer; it gets smaller.
For the big fish, she opens just right.
Two arms, one vertex—make an angle.
Spread them wider; the angle grows.
Bring them closer; it gets smaller.
The arms' directions set its size.
Each angle arm is called a ray.
From the vertex, it continues one way.
Cardboard shows just part of that ray.
Shorten the strip, don't turn it: same angle.
Two arms, one vertex—make an angle.
Spread them wider; the angle grows.
Bring them closer; it gets smaller.
The arms' directions set its size.
Big fish fits; the jaws are open just right.
Two arms, one vertex—angle found!