Find the Surface Area of a Cylinder Dave May Teaches

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Find the Surface Area of a Cylinder Dave May Teaches

David May · ⏱ 2:07 · 112 مشاهدة · 12 years ago

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the surface area of cylinder can be explained in the following simple formula 2 pi squared plus 2 pi got that i'm sorry thought said it was simple formula listen don't memorize this give me chance to explain the surface area of cylinder for you where this just makes sense okay what's cylinder cylinder is like circle that's been pulled into the third dimension and if you like look at it cylinder it's like circle on top and on bottom is another circle and the side is like rolled up rectangle so to find the surface area of cylinder you just add up three areas one of the circles plus the other circle plus the area of that rectangle let me show you how it's done let's take look at cylinder that has radius of four and that's like six tall the height is six let's find the surface area well we got to find the area of the two circles and the rectangle how do you find the area of circle it's pi squared so if the radius is 4 the area would be 16 pi sweet we suddenly just found the area two of these three shapes we just gotta find the area of the rectangle and the right area of rectangle is just base times height and already told you the height was six so we just got to find the length of this other side of the rectangle and we'll be done this is the tricky part though this the length of that other side of the rectangle is the same thing as the circumference of the circle so well the circumference of circle is diameter times pi and told you the radius was four the diameter would be eight so the circumference would be eight pi and we just found this side the other side of the rectangle so we can find the area it's eight pi times six which would be 48 pi and we've got the area of all three shapes let's add them together 16 pi plus 16 pi plus 48 pi is going to give you 80 pi that's the surface area that's how you find the surface area of cylinder