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The area of a circle can be found by multiplying the number pi by the square of the radius.
If the radius of a circle is r, write an expression that presents the area of the circle.
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The area of a circle
S = ,
where R is the radius of the circle.
See the lesson
- Area of a circle
in this site.
Also, you have free of charge online textbook in Geometry
GEOMETRY - YOUR ONLINE TEXTBOOK
in this site.