The formula for a surface area of a cylinder is [tex]2 \pi r^{2} + 2\pi rh[/tex].
For developing this formula you should consider that the surface area for a cylinder consists of the sum between the areas of circles and the rectangle, as shown in the image. Therefore, you have:
[tex]Cylinder_{surface area}= 2 * area_{circle} + area_{rectangle}\\ \\ Cylinder_{surface area}= 2 * (\pi *r^{2} ) + (b*h)\\ \\ Cylinder_{surface area}= 2 \pi r^{2} + bh\\ \\ Cylinder_{surface area}= 2 \pi r^{2} + 2\pi rh[/tex]
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