What Is an Angle?
Aligned to 4.MD.C.5 — Common Core State Standards for Mathematics.
What this lesson teaches
An angle is formed by two rays that start from the same point, called the vertex. Angle size is how far one ray is turned from the other, measured in degrees. A full turn around a circle is 360 degrees.
Worked example
Imagine a clock hand turning all the way around: that full circle is 360 degrees. If a ray turns one quarter of the way around the circle, that is one fourth of 360: 360 / 4 = 90 degrees. So a quarter turn makes a 90 degree angle.
Practice questions
- How many degrees is a half turn around a circle?
- A ray turns one third of the way around a circle. How many degrees is that?
- An angle is 1/6 of a full circle. How many degrees does it measure?
Watch the lesson
Every lesson comes with a video taught in English and Spanish — the same video the QR code in the printed workbook opens.
▶ Watch this lessonEn español
Que es un angulo?
Un angulo se forma con dos rayos que salen del mismo punto, llamado vertice. El tamano del angulo es cuanto gira un rayo respecto al otro, medido en grados. Una vuelta completa alrededor de un circulo es 360 grados.
Ejemplo: Imagina la manecilla de un reloj girando por completo: ese circulo completo es 360 grados. Si un rayo gira un cuarto de la vuelta alrededor del circulo, eso es un cuarto de 360: 360 / 4 = 90 grados. Entonces un cuarto de vuelta forma un angulo de 90 grados.
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