- #1

binbagsss

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**See image attached.**

(I've had a google but can't find anything).

I am trying to understand the expression : Rdθ.2∏Rsinθ

(I've had a google but can't find anything).

I am trying to understand the expression : Rdθ.2∏Rsinθ

**Here are my thoughts so far:**Rdθ is the width of a strip, θ being the variable changing/to integrate over, giving arise to the elements.

2∏Rsinθ must then be the length. However I don't understand this expression.

I think I understand Rdθ - it is the arc length.

*Here are my length thoughts:*From the triangle sin θ =(l/2)/R, where l is the length we are after, and l/2, because this triangle only gives half of the length we are after.

Ofc this must be wrong, as I have a ∏ unexplained.

**Many thanks to anyone who can help shed some light on this, greatly appreciated !**