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The diagram shows how the value of the function (y) is calculated from the radius (a - red) of the circle sweeping out an angle θ (theta). What does "sweeping out an angle" mean here?

Wave Properties, Waves - from A-level Physics Tutor

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JigneshbharatiWhat does "sweeping out an angle" mean here?

Imagine the radius as a solid rod like one of the spokes of a bicycle wheel.
Then imagine one end of this rod fixed in place at the center of the circle or wheel.
Imagine the rod moving around the circle like the spoke of a bicycle wheel moves around its center.

That's "sweeping out an angle". If it goes all the way around the circle it sweeps out an angle of 360 degrees. If goes only half way around the circle, it sweeps out an angle of 180 degrees. And so on.

CJ

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Thanks! Is "sweeping out" a phrasal verbs? I couldn't find the meaning in any dictionary?

JigneshbharatiIs "sweeping out" a phrasal verbs? verb?

Yes.

CJ

Why can't I find the meaning in any dictionary?

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